The non-catalytic ‘cap domain’ of a mycobacterial metallophosphoesterase regulates its expression and localization in the cell [Protein Structure and Folding]

June 25th, 2014 by Matange, N., Podobnik, M., Visweswariah, S. S.

Despite highly conserved core catalytic domains, members of the metallophosphoesterase (MPE) superfamily perform diverse and crucial functions ranging from nucleotide and nucleic acid metabolism to phospholipid hydrolysis. Unique structural elements outside of the catalytic core called ′cap domains′ are thought to provide specialization to these enzymes; however no directed study has been performed to substantiate this. The $[prime]cap domain′ of Rv0805, an MPE from M. tuberculosis, is located C-terminal to its catalytic domain, and is dispensable for the catalytic activity of this enzyme in vitro. We show here that this C-terminal extension (CTE) mediates in vivo localization of the protein to the cell membrane and cell wall, as well as modulates expression levels of Rv0805 in mycobacteria. We also demonstrate that Rv0805 interacts with the cell wall of mycobacteria possibly with the mAGP complex, by virtue of its C-terminus, a hitherto unknown property of this MPE. Using a panel of mutant proteins, we identify interactions between active site residues of Rv0805 and the CTE that determine its association with the cell wall. Finally, we show that Rv0805 and a truncated mutant devoid of the CTE, produce different phenotypic effects when expressed in mycobacteria. Our study thus provides a detailed dissection of the functions of the ′cap domain′of an MPE, and suggests that the repertoire of cellular functions of MPEs cannot be understood without exploring the modulatory effects of these sub-domains.
  • Posted in Journal of Biological Chemistry, Publications
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