2F6L

X-ray structure of Chorismate Mutase from Mycobacterium Tuberculosis

Summary for 2F6L

• Entry DOI: 10.2210/pdb2f6l/pdb
• Descriptor: Chorismate mutase (2 entities in total)
• Functional Keywords: helical, dimer, isomerase
• Biological source: Mycobacterium tuberculosis
• Total number of polymer chains: 2
• Total formula weight: 36991.02

Authors

Kim, S.K.,Howard, A.J.,Gilliland, G.L.,Reddy, P.T.,Ladner, J.E. (deposition date: 2005-11-29, release date: 2005-12-13, Last modification date: 2024-10-16)

Primary citation

Kim, S.K.,Reddy, S.K.,Nelson, B.C.,Vasquez, G.B.,Davis, A.,Howard, A.J.,Patterson, S.,Gilliland, G.L.,Ladner, J.E.,Reddy, P.T.
Biochemical and structural characterization of the secreted chorismate mutase (Rv1885c) from Mycobacterium tuberculosis H37Rv: an *AroQ enzyme not regulated by the aromatic amino acids.
J.Bacteriol., 188:8638-8648, 2006

PubMed Abstract: The gene Rv1885c from the genome of Mycobacterium tuberculosis H37Rv encodes a monofunctional and secreted chorismate mutase (*MtCM) with a 33-amino-acid cleavable signal sequence; hence, it belongs to the *AroQ class of chorismate mutases. Consistent with the heterologously expressed *MtCM having periplasmic destination in Escherichia coli and the absence of a discrete periplasmic compartment in M. tuberculosis, we show here that *MtCM secretes into the culture filtrate of M. tuberculosis. *MtCM functions as a homodimer and exhibits a dimeric state of the protein at a concentration as low as 5 nM. *MtCM exhibits simple Michaelis-Menten kinetics with a Km of 0.5 +/- 0.05 mM and a k(cat) of 60 s(-1) per active site (at 37 degrees C and pH 7.5). The crystal structure of *MtCM has been determined at 1.7 A resolution (Protein Data Bank identifier 2F6L). The protein has an all alpha-helical structure, and the active site is formed within a single chain without any contribution from the second chain in the dimer. Analysis of the structure shows a novel fold topology for the protein with a topologically rearranged helix containing Arg134. We provide evidence by site-directed mutagenesis that the residues Arg49, Lys60, Arg72, Thr105, Glu109, and Arg134 constitute the catalytic site; the numbering of the residues includes the signal sequence. Our investigation on the effect of phenylalanine, tyrosine, and tryptophan on *MtCM shows that *MtCM is not regulated by the aromatic amino acids. Consistent with this observation, the X-ray structure of *MtCM does not have an allosteric regulatory site.

PubMed: 17146044
DOI: 10.1128/JB.00441-06

Experimental method

X-RAY DIFFRACTION (1.7 Å)