Structures of apomyoglobin's various acid-destabilized forms

R. Gilmanshin, M. Gulotta, R. B. Dyer, R. H. Callender

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Abstract

The structures and the cold and hot melting thermodynamics of the acid- and salt-destabilized states of horse heart apomyoglobin (apoMb), including the E (extended) and various I forms, are studied using probes of tertiary structure (tryptophan fluorescence and FTIR spectroscopy) and secondary structure (far-UV CD and FTIR spectroscopy). These forms likely resemble early structures in the folding of the largely helical protein. Both the I and E forms retain the AGH core whereby the two ends of the protein are tied together with sufficient numbers of tertiary contacts, involving a number of hydrophobic residues, to show cooperative melting. The melting thermodynamics of E and I are distinctly different. E contains no other tertiary structure and probably little other secondary structure apart from the core. The more destabilized E form appears to contain "random" buried runs of polypeptide backbone which convert to α-helix in the I form(s). Most interestingly, E consists not of a single structure but is composed of a heterogeneous mixture of conformations, all showing corelike cooperative melting characteristics, and consisting presumably of varying contacts between the A portion of apomyoglobin and the G - H hairpin. These results bear on the energy landscape and structural features of the early part of apomyoglobin's folding pathway.

Original languageEnglish (US)
Pages (from-to)5127-5136
Number of pages10
JournalBiochemistry
Volume40
Issue number17
Publication statusPublished - May 1 2001

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ASJC Scopus subject areas

  • Biochemistry

Cite this

Gilmanshin, R., Gulotta, M., Dyer, R. B., & Callender, R. H. (2001). Structures of apomyoglobin's various acid-destabilized forms. Biochemistry, 40(17), 5127-5136.