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Conformational flexibility of angiotensin II. A carbon-13 spin-lattice relaxation study
- Source :
- Biochemistry. 14(5)
- Publication Year :
- 1975
-
Abstract
- Carbon-13 spin-lattice relaxation times (T1) have been determined for the carbon in the octapeptide hormone [5-isoleucine]-angiotensin II in aqueous solution. Two possible models for molecular motion are considered: isotropic overall motion of the hormone with internal motion of some residues and anisotropic overall molecular motion. The data are interpreted in detail using the former model. The alpha carbons of the peptide backbone are all equally restricted in their motion. The correlation time for overall molecular reorientation, calculated from an everage T1 value of 95 msec for the alpha carbons in the peptide backbone, is ca. 5 times 10-10 sec. The carbons in the side chains are more mobile than those in the peptide backbone, with the exception of the side chain of the Tyr residue which does not undergo rapid segmental motion. We propose that [5-isoleucine]-angiotensin II has a restricted backbone conformation and that the alpha carbons of the N- and C-terminal residues are constrained to nearly the same extent as the remaining alpha carbons in the peptide backbone. Chemical shift data indicate that the Pro residue adopts the trans conformation about the His-Pro bond and that the imidazole ring of His has a strong preference for the N-tau -H tautomer.
- Subjects :
- Carbon Isotopes
Time Factors
Chemistry
Protein Conformation
Angiotensin II
Relaxation (NMR)
Carbon-13
Spin–lattice relaxation
Electron Spin Resonance Spectroscopy
Ring (chemistry)
Biochemistry
Tautomer
Crystallography
Residue (chemistry)
Kinetics
Leucine
Side chain
Amino Acid Sequence
Amino Acids
Isoleucine
Mathematics
Subjects
Details
- ISSN :
- 00062960
- Volume :
- 14
- Issue :
- 5
- Database :
- OpenAIRE
- Journal :
- Biochemistry
- Accession number :
- edsair.doi.dedup.....372590e08ff943fbb0e6fe3de9e6eb14