title: The non-catalytic "cap domain" of a mycobacterial metallophosphoesterase regulates its expression and localization in the cell.
abstract: 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 cap domain of Rv0805, an MPE from Mycobacterium 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 mycolyl-arabinogalactan-peptidoglycan 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 subdomains.
authors: From the Department of Molecular Reproduction, Development, and Genetics, Indian Institute of Science, Bangalore, India 560012 and.
authors: Nishad
authors: N
authors: Matange
authors: Laboratory for Molecular Biology and Nanobiotechnology, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia.
authors: Marjetka
authors: M
authors: Podobnik
authors: From the Department of Molecular Reproduction, Development, and Genetics, Indian Institute of Science, Bangalore, India 560012 and sandhya@mrdg.iisc.ernet.in.
authors: Sandhya S
authors: SS
authors: Visweswariah
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain; D002462:Cell Membrane / Q000201:enzymology; D002473:Cell Wall / Q000201:enzymology; D000242:Cyclic AMP / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D020102:Mycobacterium smegmatis / Q000201:enzymology / Q000235:genetics; D009169:Mycobacterium tuberculosis / Q000201:enzymology* / Q000235:genetics; D010727:Phosphoric Diester Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D011994:Recombinant Proteins; D000242:Cyclic AMP; D010727:Phosphoric Diester Hydrolases
keywords: Cyclic Nucleotide; Membrane Protein; Metalloprotein; Mycobacteria; Phosphodiesterases