Biochemical characterization of argininosuccinate lyase from M-tuberculosis: significance of a c-terminal cysteine in catalysis and thermal stability

Mishra, Archita and Surolia, Avadhesha (2017) Biochemical characterization of argininosuccinate lyase from M-tuberculosis: significance of a c-terminal cysteine in catalysis and thermal stability. In: IUBMB LIFE, 69 (11). pp. 896-907.

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Abstract

Arginine biosynthesis pathway is crucial to the survival and pathogenesis of Mycobacterium tuberculosis (Mtb). Arginine is a critical amino acid that contributes to the inflection of cellular immune responses during pathogenesis. Argininosuccinate lyase from Mtb (MtArgH), the last enzyme in the pathway, catalyzes the production of arginine from argininosuccinic acid. MtArgH is an essential enzyme for the growth and survival of M. tuberculosis. We biochemically characterized MtArgH and deciphered the role of a previously unexplored cysteine (Cys(441)) residue at the C-terminal region of the protein. Chemical modification of Cys(441) completely abrogated the enzymatic activity suggesting its involvement in the catalytic mechanism. Replacement of Cys(441) to alanine showed a striking decrease in the enzymatic activity, while retaining the overall secondary to quaternary structure of the protein, hence corroborating the involvement of Cys(441) in the process of catalysis. Interestingly, replacement of Cys(441) to serine, showed significant increase in activity, as compared to the wild-type MtArgH. Inactivity of C(441)A and elevated activity of its conservative mutant ((CS)-S-441) confirmed the participation of Cys(441) in the MtArgH activity. We also, observed that (CS)-S-441 mutant has higher thermal stability and maintains significant activity at high temperatures. This is in concordance with our observation that Cys(441) in Mtb is replaced by a serine in the ArgH from thermophilic microorganisms. Furthermore, we also propose a potential feedback mechanism, wherein the Cys(441) is covalently modified to S-(2-succinyl) cysteine (succination) by one of the products, fumarate, thereby inactivating MtArgH. These insights into the mechanism of MtArgH activity unravel novel regulations of arginine biosynthetic pathway in Mtb. (c) 2017 IUBMB Life, 69(11):896-907, 2017

Item Type:	Journal Article
Publication:	IUBMB LIFE
Additional Information:	Copy right for this article belongs to the WILEY, 111 RIVER ST, HOBOKEN 07030-5774, NJ USA
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited:	17 Nov 2017 05:28
Last Modified:	17 Nov 2017 05:28
URI:	http://eprints.iisc.ac.in/id/eprint/58259

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