1L1E

Crystal Structure of Mycolic Acid Cyclopropane Synthase PcaA Complexed with S-adenosyl-L-homocysteine

Summary for 1L1E

• Entry DOI: 10.2210/pdb1l1e/pdb
• Descriptor: mycolic acid synthase, CARBONATE ION, S-ADENOSYL-L-HOMOCYSTEINE, ... (4 entities in total)
• Functional Keywords: methyltransferase, s-adenosyl-l-homocysteine cofactor, alpha/beta, structural genomics, psi, protein structure initiative, tb structural genomics consortium, tbsgc, transferase
• Biological source: Mycobacterium tuberculosis
• Cellular location: Cytoplasm (By similarity): Q7D9R5
• Total number of polymer chains: 2
• Total formula weight: 67030.19

Authors

Huang, C.-C.,Smith, C.V.,Glickman, M.S.,Jacobs Jr., W.R.,Sacchettini, J.C.,TB Structural Genomics Consortium (TBSGC) (deposition date: 2002-02-15, release date: 2002-03-06, Last modification date: 2024-02-14)

Primary citation

Huang, C.-C.,Smith, C.V.,Glickman, M.S.,Jacobs Jr., W.R.,Sacchettini, J.C.
Crystal structures of mycolic acid cyclopropane synthases from Mycobacterium tuberculosis.
J.Biol.Chem., 277:11559-11569, 2002

PubMed Abstract: Mycolic acids are major components of the cell wall of Mycobacterium tuberculosis. Several studies indicate that functional groups in the acyl chain of mycolic acids are important for pathogenesis and persistence. There are at least three mycolic acid cyclopropane synthases (PcaA, CmaA1, and CmaA2) that are responsible for these site-specific modifications of mycolic 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-A resolution, respectively. All three enzymes have a seven-stranded alpha/beta 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.

PubMed: 11756461
DOI: 10.1074/jbc.M111698200

Experimental method

X-RAY DIFFRACTION (2 Å)