Subunit dissociation and unfolding of rabbit muscle phosphofructokinase by guanidine by hydrochloride.

Published

Journal Article

The denaturation of rabbit skeletal muscle phosphofructokinase by guanidine hydrochloride has been studied using fluorescence, light scattering, and enzyme activity measurements. The transition from fully active tetramer (0.1 M potassium phosphate (pH 8.0) at 10 and 23 degrees) to unfolded polypeptide chains occurs in two phases as measured by changes in the fluorescence spectrum and light scattering of the protein: dissociation to monomers at low guanidine hydrochloride concentrations (similar to 0.8 M) followed by an unfolding of the polypeptide chains, which presumably results in a random coil state, at high concentrations of denaturant (greater than 3.5 M). The initial transition can be further divided into two distinct stages. The native enzyme is rapidly dissociated to inactive monomers which then undergo a much slower conformational change that alters the fluorescence spectrum of the protein. The dissociation is complete within 2 min and is reversible, but the conformational change requires about 2 hr for completion and is not reversible under a variety of conditions, including the presence of substrates and allosteric effectors. The conformationally altered protomer reaggregates to form a precipitate at 23 degrees, but is stable below 10 degrees. The second major phase of the denaturation is fully reversible. A simple mechanism is proposed to account for the results, and its implications for the corresponding renaturation process are discussed.

Full Text

Duke Authors

Cited Authors

  • Parr, GR; Hammes, GG

Published Date

  • April 22, 1975

Published In

Volume / Issue

  • 14 / 8

Start / End Page

  • 1600 - 1605

PubMed ID

  • 123759

Pubmed Central ID

  • 123759

International Standard Serial Number (ISSN)

  • 0006-2960

Digital Object Identifier (DOI)

  • 10.1021/bi00679a009

Language

  • eng

Conference Location

  • United States