This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Ali, S. A. Articles by Arisaka, F. Search for Related Content PubMed PubMed Citation Articles by Ali, S. A. Articles by Arisaka, F.

Reversible and Fast Association Equilibria of a Molecular Chaperone, gp57A, of Bacteriophage T4

Said A. Ali ^*, Noriyuki Iwabuchi ^*, Takuro Matsui ^*, Ken Hirota , Shun-ichi Kidokoro   , Munehito Arai ^¶ ||, Kunihiro Kuwajima ^||, Peter Schuck ^** and Fumio Arisaka ^*

^* Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Japan; Department of Bioengineering, Nagaoka University of Technology, Nagaoka, Niigata, Japan; Precision and Intelligence Laboratory, Tokyo Institute of Technology, Yokohama, Japan; Genome Science Center, RIKEN, Yokohama, Japan; ^¶ Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology, Ibaraki, Japan; ^|| Graduate School of Science, University of Tokyo, Tokyo, Japan; and ^** Division of Bioengineering and Physical Science, ORS, National Institutes of Health, Bethesda, Maryland

Correspondence: Address reprint requests to Fumio Arisaka, PhD, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan. Tel./Fax: 81-45-924-5713; E-mail: farisaka{at}bio.titech.ac.jp.

The association of a molecular chaperone, gp57A, of bacteriophage T4, which facilitates formation of the long and short tail fibers, was investigated by analytical ultracentrifugation, differential scanning microcalorimetry, and stopped-flow circular dichroism (CD) to establish the association scheme of the protein. Gp57A is an oligomeric -helix protein with 79 amino acids. Analysis of the sedimentation velocity data by direct boundary modeling with Lamm equation solutions together with a more detailed boundary analysis incorporating association schemes led us to conclude that at least three oligomeric species of gp57A are in reversible and fast association equilibria and that a 3_mer-6_mer-12_mer model described the data best. On the other hand, differential scanning microcalorimetry revealed a highly reversible two-step transition of dissociation/denaturation, both of which accompanied decrease in CD at 222 nm. The melting curve analysis revealed that it is consistent with a 6_mer-3_mer-1_mer model. The refolding/association kinetics of gp57A measured by stopped-flow CD was consistent with the interpretation that the bimolecular reaction from trimer to hexamer was preceded by a fast -helix formation in the dead-time. Trimer or hexamer is likely the functional oligomeric state of gp57A.