Zwizinski C, Wickner W
J Biol Chem. 1980 Aug 25;255(16):7973-7.
Many membrane proteins and secreted proteins are synthesized in precursor form with 15 to 30 additional NH2-terminal residues. These "leader peptides" (pre-pieces, signal peptides) are removed as these proteins cross or insert into cellular membranes. "Leader peptidase" activities which catalyze this cleavage have been detected in crude extracts and found to be dependent on membrane fractions. We now describe a 6,000-fold purification of a leader peptidase from the membranes of uninfected Escherichia coli. This leader peptidase was assayed by its ability to cleave the 23-residue leader peptide from procoat, the precursor to bacteriophage M13 coat protein. Immunoprecipitation and amino acid sequencing showed that this enzyme cleaved procoat to produce authentic coat protein. No factors other than the leader peptidase were found to be required for the conversion of procoat protein to coat protein.
许多膜蛋白和分泌蛋白以前体形式合成，带有额外的15至30个氨基末端残基。这些“前导肽”（前片段、信号肽）在这些蛋白质穿过或插入细胞膜时被去除。在粗提物中已检测到催化这种切割的“前导肽酶”活性，并且发现其依赖于膜组分。我们现在描述了从未感染的大肠杆菌膜中对一种前导肽酶进行6000倍的纯化。这种前导肽酶通过其切割来自噬菌体M13外壳蛋白前体原外壳蛋白的23个残基前导肽的能力来进行测定。免疫沉淀和氨基酸测序表明，这种酶切割原外壳蛋白以产生正宗的外壳蛋白。发现将原外壳蛋白转化为外壳蛋白除了前导肽酶外不需要其他因子。
