Prolipoprotein Diacylglyceryl Transferase LGT In Lipid Modification Biology Essay
Prolipoprotein Diacylglyceryl Transferase ( LGT ) is an of import enzyme which catalyzes the lipid alteration of bacterial lipoproteins. The importance of this enzyme as a function in bring forthing full-blown lipoprotein is widely researched. Ability of LGT is bring forthing lipoproteins to play a function in cell-cell adhesion, protein ripening and alimentary acquisition leads to the endurance and colonisation of these bacteriums within the host cell. In this study, the ability of LGT to do the virulency in gram positive bacterium is reviewed. Study on the ability to do virulency in bacteriums and the cause of pathogenicity can take to findings of remedy in diseases caused by gm positive bacteriums.
Bacterial lipoproteins are alone and omnipresent to the specific bacteriums. Lipoproteins have been identified to incorporate N-acyl Diacyl Glyceryl as their N-terminal amino acid. Tokunaga et Al. proposed the first biosynthetic tract in 1982. The survey was carried out utilizing Braun ‘s lipoprotein of Escherichia Coli, in vitro and in vivo. Tokunaga and squad demonstrated that prolipoprotein-phosphatidylglycerol glyceryl transferase catalysed the transportation of non-acylated mediety of phosphatidylglycerol ( PG ) to the sulfhydryl group of the prospective N-terminal cysteine residue in the unmodified prolipoprotein. The diacylglyceryl modified prolipoproteins is formed when one or more O-aryltransferase acylates the sn-3 and sn-2 hydroxyls of the glyceryl mediety of glycerylcysteine ( Tokunaga et al. , 1982 ) . This tract was modified Sankaran and Wu in 1994 with the findings that showed diacylglyceryl alteration of prolipoprotein occurs when diacylglyceryl mediety from PG is transferred to the cysteine residue to organize diacylglyceryl-prolipoprotein with the formation of sn-1 phosphate. The enzyme that catalyzes this reaction is prolipoprotein-phosphatidylglycerol diacylglyceyl transferase ( LGT ) ( Sankaran and Wu, 1994 ) . In the survey carried out, lgt was shown to be one of the cistrons that encodes for prolipoprotein alteration and enzyme processing. Therefore, the decision derived from the survey suggested that lgt cistron is indispensable for lipid alteration.
Figure 1: Prolipoprotein Diacylglyceryl Transferase ( LGT ) in Lipid Modification tract ( Sankaran and Wu, 1994 )
This tract is indispensable for bacterial growing, viability and cell division. Analysis of this enzyme provides information about the freshness of reaction which is catalyzed by LGT, its ubiquitousness in bacteriums and importance as the first measure in the lipid alteration tract. Lipoproteins are known to play a function in cell-cell attachment, protein ripening, cell signalling and besides alimentary acquisition ( Hamilton et al. , 2000 ) . Bacterial lipoproteins besides play a function in endurance of bacteriums within the host cell and colonisation of bacterial in the host cells ( Sutcliffe and Harrington, 2002 ; Sutcliffe and Harrington, 2004 ; Sutcliffe and Russell, 1995 ) . Therefore, understanding of the lipid alteration tract and the function of LGT is of import to find the procedures which are affected by LGT. Importantly, its function in cell-cell attachment plays a function in adhesion of bacteriums to the cells, doing its infective reaction therefore taking to the disease ( Hamilton et al. , 2000 ) ..
Harmonizing to MeSH, virulency is the grade of pathogenicity within a group of micro-organism as indicated by the human death rates or the invasion rate of micro-organism into the tissues of host. This pathogenicity capableness is determined by factors doing its invasion or human death.
Comparison with gram negative bacteriums
Relationship between the construction and map of Lipoprotein Diacylglyceryl Transferase was studied by comparing its consequence in different bacteriums and effects of mutant LGT in bacterium. To analyze the relationship between the construction and map of LGT, Qi et al. , 1995, carried out a research utilizing a ringer incorporating LGT cistron, lgt, which was isolated from Staphylococcus aureus to analyze its consequence in the bacterium.
Amino acid comparing of LGT from Staphylococcus aureus with LGT sequences of gm negative bacteriums from the GenBank database was carried out. A high degree of homology was found with LGT of Escherichia coli, Haemophilus influenzae and Salmonella thyphimurium which were antecedently cloned. A stretch of hydrophobic sections interrupted by hydrophilic sections were significantly noticed. The observation of 24 % individuality and 47 % similarity shows that S.aureus is non 100 % similar to the gm negative bacterium. This shows that the bacterium differs in the lipid alteration procedure every bit good, bespeaking the consequence of LGT on both type of bacteriums can be different.
Solid boxes represent individuality
Dashed boxes represent similarity
. . . . . . stand for the spread in the sequence
Figure 2: Amino acerb sequences of LGT from E.coli, S.typhimurium, H.influenzae and S.aureus. Amino acerb comparing of these sequences showed a 24 % individuality and 47 % similarity.
At impersonal pH, S.aureus has a net charge of +9. This is due to the copiousness of Arginine and Lysine amino acid in approximately equal sums. The other three gms negative bacteriums revealed prevailing degrees of Arginine and a few Lysine residues. Based from the comparing of cyberspace charges, LGT of S.aureus is the highest compared to those of the gm negative bacteriums.
Net Charge of LGT
Table 1: Net charge of LGT of gm positive and gram negative bacteriums at impersonal pH
The pI degree of LGT in S.aureus was about 10.40. N-terminal and the in-between part of LGT were observed to be more conserved than the C-terminal part in S.aureus. Codon use of S.aureus lgt cistron differs from the codon use of gram negative bacteriums. The lgt cistron organisation in S.aureus differs from the 1s in gm positive bacteriums. In S.aureus, thyA cistron is non following to the lgt cistron. A important stretch ( H-103-GGLIG-108 ) was identified in the S.aureus LGT enzyme. The stretch contains an invariant Histidine ( His-103 ) which shows the possible association with the calalytic activity of the LGT enzyme. The size of LGT in S.aureus is smaller than the LGT in E.coli and S.typhi by 12 aminic acids. It is nevertheless larger than the LGT in H.influenzae by 11 amino acid. Based on Chou-Fasman anticipation, LGT in S.aureus is high in I±-helix-breaking amino acid, glycine and proline. Staph aureus besides has prevailing degrees of I?-sheet construction and low degrees of I±-helix. This is nevertheless similar to the other gm negative bacteriums used in this survey.
Aim of Study
In this study, the analysis of LGT as a virulency factor will be studied peculiarly in gm positive bacteriums. To analyze the consequence of LGT on the virulency of gm positive bacteriums, analysis was done of several gms positive bacteriums. Below is the list of gram positive bacteriums which was reviewed in this study:
Gram positive bacteriums
Table 2: List of gram positive bacteriums reviewed in the study
Study of LGT in Staphylococcus aureus
Staphylococcus aureus is known to do diseases such as pneumonia, bacteriemia, osteomylitis and other skin infections. These diseases occur when Staphylococcus aureus overcomes the physical barrier and invades the tissues via contaminated medical devices or surgical lesions ( Lowy, 1998 ) . Immune system responses towards the pathogen, Staphylococcus aureus, when it invades the cells. Bacterial lipoprotein which maps as pathogen-associated molecule forms ( PAMPs ) bind to the Toll-like receptors ( TLRs ) which triggers a signaling cascade in response to the pathogens ( Aliprantis et al. , 1999 ; Brightbill et al. , 1999 ; Hirschfeld et al. , 1999 ; Medzhitov et al. , 1997 ; Medzhitov, 2001 and Yoshimura et al. , 1999 ) . In short, these bacterial lipoproteins trigger an immune response in instance of a Staphylococcus aureus infection ( Stoll et al. , 2005 ) . Bacterial lipoproteins have been observed to Aliprantis et al. , 1999 ; Brightbill et al. , 1999 ; Hirschfeld et al. , 1999 ; Norgard et al. , 1996 and Rawadi et al. , 1999 ) . Stoll and squad investigated the part of LGT towards the virulency of S.aureus by detecting the immune response of lgt mutation in the host cell ( Stoll et al. , 2005 ) . In the survey carried out, a S.aureus lgt: :ermB mutation was constructed by replacing lgt cistron with an Erythrocin immune cassette ( ermB ) . As lgt cistron was replaced, lipid alteration would non be able to take topographic point and its effects on invasion into the host cells and cytotoxic effects were observed. One of the observations from the survey includes the sum of lipoprotein detected. Most lipoproteins were found in the membrane, low degrees in the cell wall and civilization environment in which the bacterium is kept. This surface edge and lipoproteins which are released into the environment can interact with the host immune system ( Stoll et al. , 2005 ) . Epithelial cells which acts as barrier against pathogens and activate phagocytic cells by let go ofing chemokines and cytokines. A549 pneumonic type II epithelial cells were used to find the consequence of inflammatory immune response towards lgt mutation. These epithelial cells were infected with both lgt mutation S.aureus and wild-type S.aureus ( lgt cistron maps as normal ) . Initiation of IL-6, an redness activator, and IL-8, a neutrophil activator, was assessed. More cytokines were observed in the presence of lgt cistron compared to the cells with mutant lgt cistron. This shows that lipoproteins present in the cells are the cause of cytokine and chemokine initiation. Stoll and squad besides reported the absence of LGT in the host cells fails to bring on Tumour Necrosis Factor-I± ( TNF-I± ) response ( Stoll et al. , 2005 ) . Missiakas and squad besides demonstrated that mice infected with lgt mutation bacterium die quickly compared to mice with an lgt interpolation ( Missiakas et al. , 2006 ) . Lipid alteration plays a function in bring oning and immune response against S.aureus and LGT being the first measure in this procedure, decidedly plays an of import function in bring oning a response in the virulency of this gm positive bacteriums.
Study of LGT in Listeria monocytogenes
Listeria monocytogenes, a facultative intracellular pathogen is known to do food-borne disease in both worlds and animate beings ( Seeliger, 1988 ) . Listeriosis, as the disease is named leads to syndromes such has meningitis, phrenitis, abortion and sepsis. Lgt, the cardinal enzyme involved in lipoprotein processing plays a function in the virulency of L.monocytogenes. PrfA, a positive written text regulator, controls the virulency factors of Listeria monocytogenes ( Baumgartner et al. , 2007 ) . This enables the bacterium to occupy and multiply in cells despite the barriers present in mammals. The absence of Lgt impairs growing of L.monocytogenes intracellularly. This causes the release of lipoproteins in to the civilization supernatant. The high degrees of lipoproteins in the supernatant enable the designation of PrfA-dependent lipoproteins. Over look of PrfA increases the virulency factors of L.monocytogenes as observed in this survey carried out. High degree of preservation is observed for Lgt in Listeria, demoing a 98 to 100 % individuality. In the survey carried out by Baumgarter M. et Al showed that the omission of lgt cistron which encodes the Lgt enzyme, in L.monocytogenes leads to desert in the bacterial cell growing intracellularly and higher degrees of lipoprotein was detected in the civilization environment. This strengthens the fact that Lgt is needed for full virulency of L.monocytogenes. Absence of Lgt consequences in the defect in bacterial cells growing which leads to inability of the bacteriums to transport out its map. Lgt cistron was deleted by building an in-frame omission. This mutant strain was similar to the original strain in cell and settlement morphology. Baumgartner et al demonstrated the cistron omission of lgt does non impact cell growing in the encephalon bosom extract medium, a medium enabling bacterial cell growing as the growing analysis showed similarity of growing rates at the logarithmic stage. However, in nerve-racking conditions such as deficiency of foods, during cell invasion or intracellular growing, mutant lgt strain seems to hold a decreased growing compared to the wild type strain. Infection of both wild type and mutant lgt strain on the mouse fibroblast cell line showed the part of lipidation to the pathogenicity of Listeria monocytogenes. This once more shows the consequence of LGT on the ability of Listeria monocytogenes to do the disease. Consequences indicated that lgt did non interfere with motion of the bacteriums within the cells. Lgt omission besides did non impact the entry of these gms positive bacteriums into the mammalian cell lines. Interestingly, hours after the infection of mutant lgt, there were low degrees of this mutant lgt in the mouse cell line. This strengthens the observation that Lgt plays a function in intracellular growing in L.monocytogenes ( Baumgartner et al. , 2007 ) . This lgt cistron omission in L.monocytogenes showed the part of Lgt towards the virulency of the bacteriums. Lgt is one of the virulency factors in this bacterium but it has to be noted that Lgt entirely is non the cause of this bacterium ‘s pathogenecity. Another survey showed that L.monocytogenes which are depriveded of lgt cistron are non able to bring on NF-I?B activation via TLR2 initiation. Lipoproteins were shown to be ligands of TLR2, doing to play an of import function in bacteria acknowledgment during an infection by L.monocytogenes ( Machata et al. , 2008 ) .
Study of LGT in Streptococcus agalactiae
Gram positive bacteriums, Steptococcus agalactiae is categorized under the Group B Streptococcus ( GBS ) . S.agalatiae is the taking cause sepsis and meningitis in neonates ( Fluegge et al. , 2005 and Luck et al. , 2003 ) . The infection of this gm positive bacteria leads to extremely inflammatory diseases with a decease rate of about 10 % . A series of Nitric Oxide ( NO ) , cytokines and intracellular signaling intermediates is release by GBS when the host in infected in vitro ( Henneke & A ; Berner, 2006 ) . TLR2, known as a signaling molecule was found to be indispensable in a mouse theoretical account which was infected with GBS sepsis ( Mancuso et al. , 2004 ) . GBS interaction with TLR2 is helpful when in low dose but becomes fatal in higher dose ( Henneke et al. , 2005 ) . Henneke et al. , 2005 carried out a research taking to place the inflammatory molecules released by GBS which stimulates TLR2. GBS mutation which was deficient in Bacterial Lipoproteins ( BLPs ) were found to be impaired in activation of TLR2. N-terminal acylation of prelipoproteins which were mediated by LGT was indispensable to the released factors of GBS to trip TLR2, both in vitro and in vivo. LGT is among the enzymes which cause ripening of BLPs by catalysing the acylation of signal peptide lipobox. In the experiment carried out by Henneke and squad, lgt cistron was inactivated in a GBS strain which was isolated from an baby diagnosed with fatal blood poisoning. The function of protein acylation was studied in this inflammatory authority of GBS. Comparison was done between both wild-type strain and mutation with an inactivated lgt cistron. The GBS was cultured in the presence of [ 2H ] palmitate to infix the labelled acyl ground tackles into the N-terminus of lipoproteins. Sodium Dodecyl Sulphate Polyacrylamide Gel Electrophoresis ( SDS PAGE ) was carried out to divide the bacterial cell infusions. Many sets were observed in the wild-type strain of GBS and no labelled sets were detected in the lgt mutant strain of GBS, corroborating both the presence and absence of lgt in wild-type and mutated strain separately. Cell civilization supernatant with the mutated lgt GBS strain showed low inflammatory activation of RAW macrophages. This was assessed by the release of TNF ( Figure 3 ) . Wild-type strain with the presence of the lipoprotein lead to the NF-I?B activation in a TLR2 check.
Figure 3: Analysis for TNF initiation in RAW macrophages in the wild-type strain
Figure 4: Analysis for TNF initiation in RAW macrophages in the mutated lgt strain
Cytokine formation was observed in macrophages, stimulated by GBS with lgt strain ( Figure 4 ) . Therefore, ripening of BLPs affect the TLR2 activation. Interaction of GBS and TLR2 is non critical for cytokine initiation in macrophages. However, it is of import to observe this interaction at the cell-cell interface. Protein acylation is an of import procedure required for the interaction of GBS-BLPs and TLR2. This protein acylation is carried out by LGT, the enzyme studied in this research. In the presence of BLPs, GBS incorporating lipoteichoic acid ( LTA ) activates TLR2. LTA is known as an of import TLR2 agonist which binds to TLR2 and triggers its response ( 26-28 ) . LTA from lgt mutation showed small consequence compared to the LTA from the wild-type strain. BLP, a GBS merchandise, interaction with TLR2 which contributed to the GBS sepsis in mice is an early acknowledgment of GBS. This mechanism alerts the immune system during GBS sepsis. If there is deficient interaction between BLPs and TLR2, occurance of redness, organ failure or even decease can be observed ( Henneke et al, 2008 ) . In a separate survey conducted, mutated LGT enzyme did non impact cell viability of S.agalactiae, nevertheless, pleiotropic effects due to the mutated enzyme is important to the virulency of this gm positive bacteriums ( Bray et al. , 2009 ) .
Study of LGT in other gm positive bacteriums
Streptococcus equi is known to be the cause of equine distempers ( Timoney, 2004 ) ; a pharyngeal bottleneck is the upper respiratory piece of land of a Equus caballus ( Slater, 2003 ) . Hamilton and squad concluded that lipid alteration tract is the cause of S.equi pathogenecity. Study was carried out in both mouse theoretical accounts and pony theoretical accounts. Failure of mice to derive weight and early marks of equine distempers disease such as rhinal discharges, swelling of lymph nodes and fever in ponies confirmed the findings that presence of LGT is one of the virulency factors in S.equi ( Hamilton et al. , 2006 ) .
Viridan group of streptococci consist of Steptococcus sanguinis ( Carlsson, 1965 ) . S.sanguinis causes endocarditis, an infection of the valves or liner of the bosom ( Moreillon and Que, 2004 ) . Arthritic febrility occurance causes serious harm to the bosom which leads to endocarditis ( Moreillon and Que, 2004 ; Wilson et al. , 2007 ) . Mutated lgt cistron used in this survey of S.sanguinis indicated a loss of protein labelling ( Das et al. , 2009 ) . This indicated a deficiency of acylation ( Lai et al. , 1980 ) doing a defect in the virulency of S.sanguinis. The overall image of this survey indicated that LGT affects the virulency of this gm positive bacteria. Mutated signifier of this enzyme indicated the decreased virulency in S.sanguinis ( Das et al, 2009 ) .
Prolipoprotein Diacylglyceryl Transferase is an enzyme which plays an of import function in the first measure of the lipid alteration tract ( Sankaran and Wu, 1994 ) . Lipoprotein, catalyzed by LGT, plays an of import function in cell-cell adhesion ( Hamilton et al. , 2000 ) . Cell-cell adhesion is of import in bacterial attachment towards the host cells. Attachment to the host cells will enable bacteriums to go through on the virulency factors to the bacterium. Failure in LGT enzyme to map can ensue in release of lipoproteins into the civilization medium. This may do virulency doing proteins to be degraded ( Hamilton et al. , 2006 ) . Absence of lipid alteration does non impact the cell viability of L.monocytogenes ( Baumgartner et al, 2007 ) . This supports the informations shown for all S.aureus, B. subtilis and S.pneumoniae ( Leskela et al. , 1999 ; Petit et al. , 2001 and Stoll et al. , 2005 ) . Defect in LGT can impact virulency in the gm positive bacteriums but cell count of bacteriums is non affected as bacterial growing continues. In survey done utilizing S.aureus theoretical account, deficiency of lipid alteration played a function in the immune response ( Stoll et al. , 2005 ) . This indicated that defect in LGT, taking to deficiency of lipid alteration, impacting the host ‘s immune response towards the bacteriums. Loss of surface lipoproteins to play a function in cell-cell adhesion reduces acknowledgment by TLR2. This causes enhanced virulency in S.aureus despite the mutated lgt cistron ( Stoll et al. , 2005 ; Wardenburg et al. , 2005 ) . However, Streptococcus pneumoniae was shown to non exhibit much virulency in the presence of a mutated lgt cistron ( Khandavilli et al. , 2008 ) . Absence of LGT is able to impair growing of gm positive bacteriums particularly L.monocytogenes intracellularly. This will do the release of unmodified lipoproteins into the civilization supernatant enabling designation of PrfA-dependent lipoproteins. Bacteria will be able to occupy and multiply in the host cell by the designation of PrfA as it controls the virulency factors of L.monocytogenes. ( Baumgartner et al. , 2007 ) . Baumgartner et al. , 2007 besides showed that consequence of cell growing intracellularly leads to the release of lipoproteins into the cell environment, therefore, cut downing the full virulency of L.monocytogenes. TLR2 induces NF-I?B activation. However, reduced or impaired lgt cistron is unable to trip TLR2 as shown in the survey of L.monocytogenes ( Machata et al. , 2008 ) taking to impaired immune response towards the gm positive bacterial infection. Lipoprotein, being one of the of import parts of an ABC transporter system is involved in foods uptake by the gm positive bacteriums, bacterial emphasis response, and many of which is of import for bacterial growing and endurance. Unmodified or unrefined bacterial lipoproteins can take to an impaired ABC transporter system. This shows the significance of ABC transporter which contains lipoprotein to play a function in the virulency of gm positive bacteriums ( Polissi et al. , 1998 ) . Protein acylation was noted to be an of import event in the GBS-BLPs interaction with TLR2 as observed in the survey carried out in Group B Streptococcus, S.agalactiae ( Henneke et al. , 2008 ) . As protein acylation is carried out by LGT, impaired LGT can do reduced interaction with TLR2, taking to impaired virulency of S.agalactiae. To sum up, LGT play a function in geting a full-blown lipoprotein in gram positive bacteriums. Matured lipoprotein is able to do full virulency in gram positive bacteriums. Absence of this enzyme can ensue in impaired virulency. Ability to transport out the infective maps as a bacterium will be impaired. Therefore, it is of import to understand the function of LGT which synthesizes lipoproteins in order to infer therapies for bacterial infections.
LGT is an indispensable enzyme in gram positive bacteriums as it catalyzes the first measure in the lipid alteration tract giving rise to matured lipoproteins. Based on the journal reappraisals on gm positive bacteriums, LGT was shown to play a function in the virulency, grade of pathogenecitiy, in the bacterium. Absence of lgt cistron showed low degrees of bacterial pathogenicity, the ability of bacteriums to do diseases.
Further research has to be done to detect if S.aureus lgt mutation shows attenuated virulency in vivo ( Stoll et al. , 2005 ) . Further survey on bacterial lipoproteins to be used as vaccinums can be done as bacterial lipoproteins are extremely accessible to the host cells on the surface of the bacteriums ( Lei et al. , 2004 and Tettelin et al. , 2002 ) .