Mycolyltransferase from Mycobacterium leprae excludes mycolate-containing glycolipid substrates.
Trehalose dimycolate (TDM) is a major surface-exposed mycolyl glycolipid that contributes to the hydrophobic cell wall architecture of mycobacteria. Nevertheless, because of its potent adjuvant functions, pathogenic mycobacteria appear to have evolved an evasive maneuver to down-regulate TDM expression within the host. We have shown previously that Mycobacterium tuberculosis (M.tb) and Mycobacterium avium (M.av), replace TDM with glucose monomycolate (GMM) by borrowing host-derived glucose as an alternative substrate for the FbpA mycolyltransferase. Mycobacterium leprae (M.le), the causative microorganism of human leprosy, is also known to down-regulate TDM expression in infected tissues, but the function of its mycolyltransferases has been poorly analysed. We found that, unlike M.tb and M.av FbpA enzymes, M.av FbpA was unexpectedly inefficient in transferring alpha-branched mycolates, resulting in impaired production of both TDM and GMM. Molecular modelling and mutational analysis indicated that a bulky side chain of leucine at position 130 of M.le FbpA obstructed the intramolecular tunnel that was proposed to accommodate the alpha-branch portion of the substrates. Notably, even after a highly reductive evolution, M.le FbpA remained functional in terms of transferring unbranched acyl chains, suggesting a role that is distinct from that as a mycolyltransferase.
Nakao
Hitomi
H
Laboratory of Cell Regulation, Institute for Virus Research, Kyoto University, Kyoto 606-8502, Japan.
Matsunaga
Isamu
I
Morita
Daisuke
D
Aboshi
Takako
T
Harada
Toshiyuki
T
Nakagawa
Yoshiaki
Y
Mori
Naoki
N
Sugita
Masahiko
M
D000217:Acyltransferases / Q000378:metabolism*; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism; D006017:Glycolipids / Q000378:metabolism*; D007700:Kinetics; D007930:Leucine / Q000378:metabolism; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000378:metabolism; D009166:Mycobacterium leprae / Q000201:enzymology*; D009171:Mycolic Acids / Q000378:metabolism*; D011485:Protein Binding; D013379:Substrate Specificity
D001426:Bacterial Proteins; D005227:Fatty Acids; D006017:Glycolipids; D050505:Mutant Proteins; D009171:Mycolic Acids; D000217:Acyltransferases; D007930:Leucine