Linked Life Data

6998977

Source:http://linkedlifedata.com/resource/pubmed/id/6998977

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
3
pubmed:dateCreated
1980-12-18
pubmed:abstractText
Resonance positions and intensities of the C(2) protons of histidyl residues (His 43 His 106) were followed in the NMR spectrum of a protein, Streptomyces subtilisin inhibitor (MW 23,000), in the pH range 2-9 at 30 degrees C, in order to clarify the microenvironment of the individual histidyl residues and the acid denaturation processes of the protein. The large difference in the 1H-2H exchange rate between the C(2) protons of the two histidyl residues indicates that, whereas His 106 is well exposed to the solvent, His 43 is highly shielded from the solvent. Protonation of His 106 occurs in the pH range 5-9, giving a pKa of 6.0 +/- 0.1. In contrast, His 43 can not be protonated in the native conformation, but is protonation occurs simultaneously with the acid denaturation of the protein in a narrow pH range 2.7-3.6, with pHmid of transition at 3.25. On the other hand, the denaturation of the His 106 environment starts at pH 5.0 and finishes at pH 2.7 with pHmid of transition at 3.7. The denaturation transitions are reversible with pH for both His 43 and His 106, but the rates of these transitions are slow (less than 25 s-1). The Hill coefficient for the His 106 transition was found to be 0.9 +/- 0.1 in the pH range 3.5-5.0, but to be distinctively larger than unity below pH 3.5. On the other hand, the Hill coefficient for the His 43 transition was found to be 4.4 +/- 0.6 for the whole range of transition (pH 2.7-3.6). These results combined with available information about the crystal structure lead us to conclude that the transition of His 106 in the pH range 3.5-5.0 represents a local denaturation caused by the protonation of one neighboring residue, probably Glu 102, whereas the transition of His 43 occurs as a result of cooperative protonation of several residues probably including Phe 113 and Asp 52, and is a denaturation step accompanied by the destruction of the major hydrophobic core.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Sep
pubmed:issn
0021-924X
pubmed:author
pubmed:issnType
Print
pubmed:volume
88
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
789-96
pubmed:dateRevised
2007-12-19
pubmed:meshHeading
pubmed:year
1980
pubmed:articleTitle
Acid denaturation steps of Streptomyces subtilisin inhibitor. A proton magnetic resonance study of individual histidine environment.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't