Document Detail

Titration behavior of individual tyrosine residues of myoglobins from sperm whale, horse, and red kangaroo.
MedLine Citation:
PMID:  8455     Owner:  NLM     Status:  MEDLINE    
The titration behavior of individual tyrosine residues of myoglobins has been studied by observing the pH dependence of the chemical shifts of Czeta and Cgamma of these residues in natural abundance of 13C Fourier transform NMR spectra (at 15.18 MHz, in 20-mm sample tubes, at 37 degrees) of cyanoferrimyoglobins from sperm whale, horse, and red kangaroo. A comparison of the pH dependence of the spectra of the three proteins yielded specific assignments for the resonance of Tyr-151 (sperm whale) and Tyr-103 (sperm whale and horse). Selective proton decoupling yielded specific assignments for Czeta of Tyr-146 of the cyanoferrimyoglobins from horse and kangaroo, but not the corresponding assignment for sperm whale. The pH dependence of the chemical shifts indicated that only Tyr-151 and Tyr-103 are titratable tyrosine residues. Even at pH 12, Tyr-146 did not begin to titrate. The titration behavior of C zeta and Cgamma of Tyr-151 of sperm whale cyanoferrimyoglobin yielded a single pK value of 10.6. The pH dependence of the chemical shift of each of the resonances of Tyr-103 of the cyanoferrimyoglobins from horse and sperm whale could not be fitted with the use of a single pK value, but was consistent with two pK values (about 9.8 and 11.6). Furthermore, the resonances of Czeta and Cgamma of Tyr-103 broadened at high pH. The titration behavior of the tyrosines of sperm whale carbon monoxide myoglobin and horse ferrimyoglobin was also examined. A comparison of all the experimental results indicated that Tyr-151 is exposed to solvent, Tyr-146 is not exposed, and Tyr-103 exhibits intermediate behavior. These results for myoglobins in solution are consistent with expectations based on the crystal structure.
D J Wilbur; A Allerhand
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  251     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  1976 Sep 
Date Detail:
Created Date:  1976-11-01     Completed Date:  1976-11-01     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  5187-94     Citation Subset:  IM    
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MeSH Terms
Binding Sites
Cetacea / metabolism*
Horses / metabolism*
Hydrogen-Ion Concentration
Macropodidae / metabolism*
Magnetic Resonance Spectroscopy
Marsupialia / metabolism*
Protein Binding
Protein Conformation
Tyrosine / analysis
Whales / metabolism*
Reg. No./Substance:
0/Cyanides; 0/Myoglobin; 55520-40-6/Tyrosine

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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