3C8Z

The 1.6 A Crystal Structure of MshC: The Rate Limiting Enzyme in the Mycothiol Biosynthetic Pathway

Summary for 3C8Z

• Entry DOI: 10.2210/pdb3c8z/pdb
• Related: 1li5 1u0b
• Descriptor: Cysteinyl-tRNA synthetase, ZINC ION, SULFATE ION, ... (7 entities in total)
• Functional Keywords: cysteine ligase, rossmann fold, cys-sa inhibitor, zinc binding, atp-binding, aminoacyl-trna synthetase, nucleotide-binding, protein biosynthesis, ligase
• Biological source: Mycobacterium smegmatis
• Total number of polymer chains: 2
• Total formula weight: 93524.49

Authors

Tremblay, L.W.,Fan, F.,Vetting, M.W.,Blanchard, J.S. (deposition date: 2008-02-14, release date: 2008-12-30, Last modification date: 2024-04-03)

Primary citation

Tremblay, L.W.,Fan, F.,Vetting, M.W.,Blanchard, J.S.
The 1.6 A crystal structure of Mycobacterium smegmatis MshC: the penultimate enzyme in the mycothiol biosynthetic pathway.
Biochemistry, 47:13326-13335, 2008

PubMed Abstract: Mycobacterium smegmatis MshC catalyzes the ATP-dependent condensation of GlcN-Ins and l-cysteine to form l-Cys-GlcN-Ins, the penultimate step in mycothiol biosynthesis. Attempts to crystallize the native, full-length MshC have been unsuccessful. However, incubation of the enzyme with the cysteinyl adenylate analogue, 5'-O-[N-(l-cysteinyl)-sulfamonyl]adenosine (CSA), followed by a 24-h limited trypsin proteolysis yielded an enzyme preparation that readily crystallized. The three-dimensional structure of MshC with CSA bound in the active site was solved and refined to 1.6 A. The refined structure exhibited electron density corresponding to the entire 47 kDa MshC molecule, with the exception of the KMSKS loop (residues 285-297), a loop previously implicated in the formation of the adenylate in related tRNA synthases. The overall tertiary fold of MshC is similar to that of cysteinyl-tRNA synthetase, with a Rossmann fold catalytic domain. The interaction of the thiolate of CSA with a zinc ion at the base of the active site suggests that the metal ion participates in amino acid binding and discrimination. A number of active site residues were observed to interact with the ligand, suggesting a role in substrate binding and catalysis. Analysis utilizing modeling of the proteolyzed loop and GlcN-Ins docking, as well as the examination of sequence conservation in the active site suggests similarities and differences between cysteinyl-tRNA synthetases and MshC in recognition of the substrates for their respective reactions.

PubMed: 19053270
DOI: 10.1021/bi801708f

Experimental method

X-RAY DIFFRACTION (1.6 Å)