title: Mycobacterium tuberculosis UsfX (Rv3287c) exhibits novel nucleotide binding and hydrolysis properties.
abstract: The Mycobacterium tuberculosis UsfX protein is an anti-sigma factor which regulates its cognate sigma factor SigF. UsfX shares low sequence homology with other anti-sigma factors making it difficult to identify the nucleotide binding site and characterize its properties. We have identified that the NTP binding site occurs close to Trp106 and the area around the nucleotide binding site is predominantly negatively charged. UsfX binds to a variety of nucleotides unlike other reported anti-sigma factors and exhibits an unusual dual NTPase activity. In silico computational experiments have identified a XGSFS motif close to the nucleotide binding site for metal ion binding. This motif is analogous to the DXSXS motif reported earlier in the human integrin CR3 protein superfamily. Overall, the experiments suggest that the M. tuberculosis UsfX represents a distinct anti-sigma factor family with a novel nucleotide binding motif.
authors: Molecular & Structural Biology Division, Central Drug Research Institute, P.O. Box 173, Chattar Manzil, Mahatma Gandhi Marg, Lucknow, Uttar Pradesh 226001, India.
authors: Shuja Shafi
authors: SS
authors: Malik
authors: Amit
authors: A
authors: Luthra
authors: Sandeep Kumar
authors: SK
authors: Srivastava
authors: Ravishankar
authors: R
authors: Ramachandran
mesh_terms: D020816:Amino Acid Motifs; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D006868:Hydrolysis; D009169:Mycobacterium tuberculosis / Q000378:metabolism*; D043583:Nucleoside-Triphosphatase / Q000737:chemistry / Q000378:metabolism*; D009711:Nucleotides / Q000378:metabolism*; D011487:Protein Conformation; D012808:Sigma Factor / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D009711:Nucleotides; C080358:RsbW protein, bacteria; D012808:Sigma Factor; D043583:Nucleoside-Triphosphatase