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Solution structure and backbone dynamics of component IV Glycera dibranchiata monomeric hemoglobin-CO. Biochemistry 1998 Aug 04;37(31):10906-19

Date

08/07/1998

Pubmed ID

9692983

DOI

10.1021/bi980810b

Scopus ID

2-s2.0-0032483048   26 Citations

Abstract

The solution structure and backbone dynamics of the recombinant, ferrous CO-ligated form of component IV monomeric hemoglobin from Glycera dibranchiata (GMH4CO) have been characterized by NMR spectroscopy. Distance geometry and simulated annealing calculations utilizing a total of 2550 distance and torsion angle constraints yielded an ensemble of 29 structures with an overall average backbone rmsd of 0.48 A from the average structure. Differences between the solution structure and a related crystal structure are confined to regions of lower precision in either the NMR or X-ray structure, or in regions where the amino acid sequences differ. 15N relaxation measurements at 76.0 and 60.8 MHz were analyzed with an extended model-free approach, and revealed low-frequency motions in the vicinity of the heme, concentrated in the F helix. Amide proton protection factors were obtained from H-D amide exchange measurements on 15N-labeled protein. Patterns in the backbone dynamics and protection factors were shown to correlate with regions of heterogeneity and disorder in the ensemble of NMR structures and with large crystallographic B-factors in the X-ray structures. Surprisingly, while the backbone atoms of the F helix have higher rmsds and larger measures of dynamics on the microsecond to millisecond time scale than the other helices, amide protection factors for residues in the F helix were observed to be similar to those of the other helices. This contrasts with H-D amide exchange measurements on sperm whale myoglobin which indicated low protection for the F helix (S. N. Loh and B. F. Volkman, unpublished results). These results for GMH4 suggest a model in which the F helix undergoes collective motions as a relatively rigid hydrogen-bonded unit, possibly pivoting about a central position near residue Val87.

Author List

Volkman BF, Alam SL, Satterlee JD, Markley JL

Author

Brian F. Volkman PhD Professor in the Biochemistry department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Amino Acid Sequence
Animals
Carbon Monoxide
Crystallography, X-Ray
Hemoglobins
Hydrogen
Macromolecular Substances
Models, Molecular
Molecular Sequence Data
Nitrogen Isotopes
Nuclear Magnetic Resonance, Biomolecular
Polychaeta
Protein Conformation
Protein Structure, Secondary
Solutions
Thermodynamics
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