TY - JOUR
T1 - Crystal structures of mycolic acid cyclopropane synthases from Mycobacterium tuberculosis
AU - Huang, Chih Chin
AU - Smith, Clare V.
AU - Glickman, Michael S.
AU - Jacobs, William R.
AU - Sacchettini, James C.
PY - 2002/3/29
Y1 - 2002/3/29
N2 - Mycolic acids are major components of the cell wall of Mycobacterium tuberculosis. Several studies indicate that functional groups in the acyl chain of mycotic acids are important for pathogenesis and persistence. There are at least three mycotic acid cyclopropane synthases (PcaA, CmaA1, and CmaA2) that are responsible for these site-specific modifications of mycotic acids. To derive information on the specificity and enzyme mechanism of the family of proteins, the crystal structures of CmaA1, CmaA2, and PcaA were solved to 2-, 2-, and 2.65-Å resolution, respectively. All three enzymes have a seven-stranded α/β fold similar to other methyltransferases with the location and interactions with the cofactor S-adenosyl-L-methionine conserved. The structures of the ternary complexes demonstrate the position of the mycolic acid substrate binding site. Close examination of the active site reveals electron density that we believe represents a bicarbonate ion. The structures support the hypothesis that these enzymes catalyze methyl transfer via a carbocation mechanism in which the bicarbonate ion acts as a general base. In addition, comparison of the enzyme structures reveals a possible mechanism for substrate specificity. These structures provide a foundation for rational-drug design, which may lead to the development of new inhibitors effective against persistent bacteria.
AB - Mycolic acids are major components of the cell wall of Mycobacterium tuberculosis. Several studies indicate that functional groups in the acyl chain of mycotic acids are important for pathogenesis and persistence. There are at least three mycotic acid cyclopropane synthases (PcaA, CmaA1, and CmaA2) that are responsible for these site-specific modifications of mycotic acids. To derive information on the specificity and enzyme mechanism of the family of proteins, the crystal structures of CmaA1, CmaA2, and PcaA were solved to 2-, 2-, and 2.65-Å resolution, respectively. All three enzymes have a seven-stranded α/β fold similar to other methyltransferases with the location and interactions with the cofactor S-adenosyl-L-methionine conserved. The structures of the ternary complexes demonstrate the position of the mycolic acid substrate binding site. Close examination of the active site reveals electron density that we believe represents a bicarbonate ion. The structures support the hypothesis that these enzymes catalyze methyl transfer via a carbocation mechanism in which the bicarbonate ion acts as a general base. In addition, comparison of the enzyme structures reveals a possible mechanism for substrate specificity. These structures provide a foundation for rational-drug design, which may lead to the development of new inhibitors effective against persistent bacteria.
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U2 - 10.1074/jbc.M111698200
DO - 10.1074/jbc.M111698200
M3 - Article
C2 - 11756461
AN - SCOPUS:0037192859
SN - 0021-9258
VL - 277
SP - 11559
EP - 11569
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 13
ER -