title: Conformational changes of PYP monitored by diffusion coefficient: effect of N-terminal alpha-helices.
abstract: Conformational changes in the light illuminated intermediate (pB) of photoactive yellow protein (PYP) were studied from a viewpoint of the diffusion coefficient (D) change of several N-truncated PYPs, which lacked the N-terminal 6, 15, or 23 amino acid residues (T6, T15, and T23, respectively). For intact PYP (i-PYP), D of pB (D(pB)) was approximately 11% lower than that (D(pG)) of the ground state (pG) species. The difference in D (D(pG) - D(pB)) decreased upon cleavage of the N-terminal region in the order of i-PYP>T6>T15>T23. This trend clearly showed that conformational change in the N-terminal group is the main reason for the slower diffusion of pB. This slower diffusion was interpreted in terms of the unfolding of the two alpha-helices in the N-terminal region, increasing the intermolecular interactions due to hydrogen bonding with water molecules. The increase in friction per one residue by the unfolding of the alpha-helix was estimated to be 0.3 x 10(-12) kg/s. The conformational change in the N-terminal group upon photoillumination is discussed.
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Javaid Shahbaz
authors.initials: JS
authors.lastname: Khan
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Imamoto
authors.forename: Miki
authors.initials: M
authors.lastname: Harigai
authors.forename: Mikio
authors.initials: M
authors.lastname: Kataoka
authors.forename: Masahide
authors.initials: M
authors.lastname: Terazima
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000528:radiation effects*; D004058:Diffusion; D004307:Dose-Response Relationship, Radiation; D008027:Light; D020283:Photoreceptors, Microbial / Q000737:chemistry* / Q000528:radiation effects*; D011487:Protein Conformation / Q000528:radiation effects; D017433:Protein Structure, Secondary / Q000528:radiation effects; D011829:Radiation Dosage; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; D020283:Photoreceptors, Microbial; C050162:photoactive yellow protein, Bacteria