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 αB-αC interfaces in the BC2 trimer and additional αC-αC 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.
|Number of pages||11|
|Journal||Journal of Biological Chemistry|
|Publication status||Published - 25 Dec 1993|
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