Open AccessThe Subunits of Rabbit‐Muscle Phosphofructokinase
Author(s) -
WALKER Ian D.,
HARRIS J. Ieuan,
RUNSWICK Michael J.,
HUDSON Peter
Publication year - 1976
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1976.tb10785.x
Subject(s) - phosphofructokinase , cysteine , protein subunit , biochemistry , peptide , arginine , peptide sequence , sequence (biology) , chemistry , biology , amino acid , enzyme , glycolysis , gene
Rabbit muscle phosphofructokinase uniformly carboxymethylated with iodo[2‐ 14 C]acetate consists of subunits with a molecular weight of 80000 ± 5000. The subunit polypeptide chain contains 16 and 52 residues respectively of cysteine and arginine and, contrary to previous results, peptide mapping experiments gave no indication that phosphofructokinase chains yield fewer than the expected numbers of cysteine and arginine containing peptides. To test further for the possible occurrence of repeat sequences within a single subunit chain, cysteine‐containing peptides were isolated and sequenced from tryptic and thermolytic digests of s‐[2‐ 14 C]carbdxymethylated phosphofructokinase. In all, 15 different cysteine sequences (comprising a total of 104 residues) were identified, showing that not more than one of an expected 16 cysteinecontaining sequences is repeated, and that the subunits in phosphofructokinase are of unique sequence along their entire length. The near quantitative isolation of several cysteine‐containing peptides shows further that all subunits are of similar if not identical sequence.