Titration behavior of individual tyrosine residues of myoglobins from sperm whale, horse, and red kangaroo.
Abstract: 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.
Publication Date: 1976-09-10 PubMed ID: 8455
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- Comparative Study
- Journal Article
- Research Support
- U.S. Gov't
- Non-P.H.S.
- Research Support
- U.S. Gov't
- P.H.S.
Summary
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This research explores the behavior of specific tyrosine residues in the protein myoglobin from three different species during titration, a process used to study pH dependence. Results suggest contrasting exposure to solvent among different residues reflecting their roles within myoglobin’s structure.
Research Methodology
- The study observed the titration behavior of individual tyrosine residues within myoglobins, specifically looking into the pH dependence of chemical shifts of Czeta and Cgamma.
- This observation was carried out on myoglobin from three different sources: sperm whale, horse, and red kangaroo.
- The myoglobin used were in the form of cyanoferrimyoglobins, a specific variant of myoglobin. These were studied using NMR (Nuclear Magnetic Resonance) spectra at specific conditions.
Results
- The study identified specific resonance for Tyr-151 (tyrosine 151) and Tyr-103 in sperm whale and horse myoglobin.
- For Tyr-146 in horse and kangaroo myoglobin, specific Czeta were assigned. However, the same was not established for the sperm whale variant.
- The pH-related chemical shifts indicated that only Tyr-151 and Tyr-103 are titratable residues, meaning they respond to changes in pH.
- The Tyr-146 residue did not exhibit any titration, even at high pH levels.
Titration Behavior
- The behavior of Tyr-151 in sperm whale yielded a single pK value of 10.6. pK values represent the pH at which a chemical species will deprotonate or lose a hydrogen ion.
- The pH dependence of the resonance of Tyr-103 could not be represented with a single pK value, suggesting that it responded to pH changes in more than one way.
- Czeta and Cgamma of Tyr-103 were observed to broaden at high pH.
Conclusions
- The study showed that Tyr-151 is exposed to solvent, implying that it is likely on the outer section of the protein molecule.
- Tyr-146 is not exposed, suggesting that it is tucked away inside the protein structure.
- Tyr-103 demonstrates intermediate behavior, indicating it could be located closer to the surface, but not fully exposed.
- The researchers concluded that these findings are consistent with what was expected based on the known crystal structure of the proteins.
Cite This Article
APA
Wilbur DJ, Allerhand A.
(1976).
Titration behavior of individual tyrosine residues of myoglobins from sperm whale, horse, and red kangaroo.
J Biol Chem, 251(17), 5187-5194.
Publication
Researcher Affiliations
MeSH Terms
- Animals
- Binding Sites
- Cetacea / metabolism
- Cyanides
- Horses / metabolism
- Hydrogen-Ion Concentration
- Macropodidae / metabolism
- Magnetic Resonance Spectroscopy
- Marsupialia / metabolism
- Myoglobin
- Protein Binding
- Protein Conformation
- Tyrosine / analysis
- Whales / metabolism
Citations
This article has been cited 4 times.- Oktaviani NA, Pool TJ, Kamikubo H, Slager J, Scheek RM, Kataoka M, Mulder FA. Comprehensive determination of protein tyrosine pKa values for photoactive yellow protein using indirect 13C NMR spectroscopy. Biophys J 2012 Feb 8;102(3):579-86.
- Mizuno H, Mal TK, Wälchli M, Fukano T, Ikura M, Miyawaki A. Molecular basis of photochromism of a fluorescent protein revealed by direct 13C detection under laser illumination. J Biomol NMR 2010 Dec;48(4):237-46.
- Mizuno H, Mal TK, Wälchli M, Kikuchi A, Fukano T, Ando R, Jeyakanthan J, Taka J, Shiro Y, Ikura M, Miyawaki A. Light-dependent regulation of structural flexibility in a photochromic fluorescent protein. Proc Natl Acad Sci U S A 2008 Jul 8;105(27):9227-32.
- Rabenstein B, Knapp EW. Calculated pH-dependent population and protonation of carbon-monoxy-myoglobin conformers. Biophys J 2001 Mar;80(3):1141-50.
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