Walker I D, Harris J I, Runswick M J, Hudson P
Eur J Biochem. 1976 Sep;68(1):255-69. doi: 10.1111/j.1432-1033.1976.tb10785.x.
Rabbit muscle phosphofructokinase uniformly carboxymethylated with iodo[2-14C]acetate consists of subunits with a molecular weight of 80 000 +/- 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-[2-14C]carboxymethylated 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 cysteine-containing sequences is repeated, and that the subunits of 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.
用碘代[2-¹⁴C]乙酸均匀羧甲基化的兔肌肉磷酸果糖激酶由分子量为80000±5000的亚基组成。亚基多肽链分别含有16个和52个半胱氨酸和精氨酸残基，与先前的结果相反，肽图谱实验没有表明磷酸果糖激酶链产生的含半胱氨酸和精氨酸的肽的数量少于预期数量。为了进一步测试单个亚基链内可能存在的重复序列，从s-[2-¹⁴C]羧甲基化磷酸果糖激酶的胰蛋白酶和嗜热菌蛋白酶消化物中分离出含半胱氨酸的肽并进行测序。总共鉴定出15种不同的半胱氨酸序列（总共104个残基），表明预期的16个含半胱氨酸序列中不超过一个是重复的，并且磷酸果糖激酶的亚基在其整个长度上具有独特的序列。几种含半胱氨酸肽的近乎定量的分离进一步表明，所有亚基即使不是完全相同的序列，也是相似的。
