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A study of the acid molten globule state of the histidine-containing proteins (HPr) from Escherichia coli and Bacillus subtilis

By Susanna Sroka


Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to, referencing the URI of the item.Includes bibliographical references: p. 77-81.Issued also on microfiche from Lange Micrographics.The salt-induced transition of the low pH forms of the histidine-containing proteins (HPr) from Escherichia coli, Bacillus subtilis and two mutants from the ecHPr protein, K45E and F22W by Na2SO4 and NaCl indicate these proteins refold to a compact intermediate (IA) with characteristics of the molten globule. The salt-induced refolding was monitored at 25 'C by far-UV circular dichroism (CD) and fluorescence of ANS (1-anilino-8-naphthalene sulfonate) and NPN (N-phenyl-naphthylamine) binding. The ecHPr F22W mutant was further monitored at 25 'C by intrinsic fluorescence of the tryptophan fluorophore. In all cases, the sulfate anion was more effective than the chloride anion in producing the IA state. However, the refolding is not a two-state process as indicated by the far-UV CD and intrinsic fluorescence transition curves of ecHPr F22W. The midpoint salt concentrations of the transition indicate that the mechanism by which anions produce the IA state involves: i) charge screening, ii) water structuring, iii) the ionic size of the anion and its electron distribution, iv) the environment of the protein surface, and v) other conditions such as, another cosolvent (fluorescent probes)

Topics: biochemistry., Major biochemistry.
Publisher: Texas A&M University
Year: 1997
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