title: Nucleotide-induced conformational change in the catalytic subunit of the phosphate-specific transporter from M. tuberculosis: implications for the ATPase structure.
abstract: The nucleotide binding subunit of the phosphate-specific transporter (PstB) from Mycobacterium tuberculosis is a member of the ABC family of permeases, which provides energy for transport through ATP hydrolysis. We utilized the intrinsic fluorescence of the single tryptophan containing protein to study the structural and conformational changes that occur upon nucleotide binding. ATP binding appeared to lead to a conformation in which the tryptophan residue had a higher degree of solvent exposure and fluorescence quenching. Substantial alteration in the proteolysis profile of PstB owing to nucleotide binding was used to decipher conformational change in the protein. In limited proteolysis experiments, we found that ATP or its nonhydrolyzable analog provided significant protection of the native protein, indicating that the effect of nucleotide on PstB conformation is directly associated with nucleotide binding. Taken together, these results indicate that nucleotide binding to PstB is accompanied by a global conformational change of the protein, which involves the helical domain from Arg137 to Trp150. Results reported here provide evidence that the putative movement of the alpha-helical sub-domain relative to the core sub-domain, until now only inferred from X-ray structures and modeling, is indeed a physiological phenomenon and is nucleotide dependent.
authors.affiliation: Institute of Microbial Technology, Sector 39 A, Chandigarh 160036, India.
authors.forename: Sankalp
authors.initials: S
authors.lastname: Gupta
authors.forename: Pradip K
authors.initials: PK
authors.lastname: Chakraborti
authors.forename: Dibyendu
authors.initials: D
authors.lastname: Sarkar
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000378:metabolism*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D020134:Catalytic Domain; D005453:Fluorescence; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000201:enzymology*; D009711:Nucleotides / Q000494:pharmacology*; D028061:Phosphate Transport Proteins / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation / Q000187:drug effects; D016415:Sequence Alignment; D014364:Tryptophan / Q000378:metabolism
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D009711:Nucleotides; D028061:Phosphate Transport Proteins; D014364:Tryptophan; D000251:Adenosine Triphosphatases; C120060:phosphate import ATP-binding protein, Bacteria