The hemoglobins of the bullfrog, Rana catesbeiana - The cDNA-derived amino acid sequences of the α chains of adult hemoglobins B and C: Their roles in deoxygenation-induced aggregation

David J. Smith, Hao Zhu, Prasanna Kolatkar, Lei Ting Tam, Thomas O. Baldwin, Bruce A. Roe, Robert H. Broyles, Austen F. Riggs

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Abstract

The adult bullfrog (Rana catesbeiana) has two major tetrameric hemoglobins, B and C, which share a common β chain but have different α chains. Components B and C associate upon deoxygenation to form a complex of the form BC2, a trimer of tetramers that depends on contacts between the αB and αC chains. Nucleotide sequences of cDNA transcripts for these chains have been determined. Transcripts were identified by analysis of the amino acid compositions of the tryptic peptides of the components and by partial amino acid sequencing. These results, together with the amino acid sequence of the β chain (Tam, L.-T., Gray, G. P., and Riggs, A. F. (1986) J. Biol. Chem. 261, 8290-8294), permit an analysis of the structures of the α2β2 tetramers of hemoglobins B and C. Molecular modeling suggests possible residues at the αBC interfaces in the BC2 trimer and additional αCC contacts that would form a closed ring of six α chain subunits that would further stabilize the BC2 trimer. Phylogenetic analysis of the αB sequence suggests that it may be a "tadpole" chain, the temporal expression of which has shifted from larva to adult.

Original languageEnglish
Pages (from-to)26961-26971
Number of pages11
JournalJournal of Biological Chemistry
Volume268
Issue number36
Publication statusPublished - 25 Dec 1993
Externally publishedYes

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ASJC Scopus subject areas

  • Biochemistry

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