Broome-Smith J K, Edelman A, Yousif S, Spratt B G
Eur J Biochem. 1985 Mar 1;147(2):437-46. doi: 10.1111/j.1432-1033.1985.tb08768.x.
Penicillin-binding proteins 1A and 1B of Escherichia coli are the major peptidoglycan transglycosylase-transpeptidases that catalyse the polymerisation and insertion of peptidoglycan precursors into the bacterial cell wall during cell elongation. The nucleotide sequence of a 2764-base-pair fragment of DNA that contained the ponA gene, encoding penicillin-binding protein 1A, was determined. The sequence predicted that penicillin-binding protein 1A had a relative molecular mass of 93 500 (850 amino acids). The amino-terminus of the protein had the features of a signal peptide but it is not known if this peptide is removed during insertion of the protein into the cytoplasmic membrane. The nucleotide sequence of a 2758-base-pair fragment of DNA that contained the ponB gene, encoding penicillin-binding protein 1B, was also determined. Penicillin-binding protein 1B consists of two major components which were shown to result from the use of alternative sites for the initiation of translation. The large and small forms of penicillin-binding protein 1B were predicted to have relative molecular masses of 94 100 and 88 800 (844 and 799 amino acids). The amino acid sequences of penicillin-binding proteins 1A and 1B could be aligned if two large gaps were introduced into the latter sequence and the two proteins then showed about 30% identity. The amino acid sequences of the proteins showed no extensive similarity to the sequences of penicillin-binding proteins 3 or 5, or to the class A or class C beta-lactamases. Two short regions of amino acid similarity were, however, found between penicillin-binding proteins 1A and 1B and the other penicillin-binding proteins and beta-lactamases. One of these included the predicted active-site serine residue which was located towards the middle of the sequences of penicillin-binding proteins 1A, 1B and 3, within the conserved sequence Gly-Ser-Xaa-Xaa-Lys-Pro. The other region was 19-40 residues to the amino-terminal side of the active-site serine and may be part of a conserved penicillin-binding site in these proteins.
大肠杆菌的青霉素结合蛋白1A和1B是主要的肽聚糖转糖基酶-转肽酶，在细胞伸长过程中催化肽聚糖前体聚合并插入细菌细胞壁。测定了包含编码青霉素结合蛋白1A的ponA基因的一段2764个碱基对的DNA片段的核苷酸序列。该序列预测青霉素结合蛋白1A的相对分子质量为93500（850个氨基酸）。该蛋白的氨基末端具有信号肽的特征，但尚不清楚该肽在蛋白插入细胞质膜过程中是否被去除。还测定了包含编码青霉素结合蛋白1B的ponB基因的一段2758个碱基对的DNA片段的核苷酸序列。青霉素结合蛋白1B由两个主要成分组成，已证明这是由于使用了翻译起始的替代位点所致。预测青霉素结合蛋白1B的大、小形式的相对分子质量分别为94100和88800（844和799个氨基酸）。如果在青霉素结合蛋白1B的序列中引入两个大的缺口，那么青霉素结合蛋白1A和1B的氨基酸序列就可以比对，此时这两种蛋白显示出约30%的同一性。这些蛋白的氨基酸序列与青霉素结合蛋白3或5的序列，或与A类或C类β-内酰胺酶的序列没有广泛的相似性。然而，在青霉素结合蛋白1A和1B与其他青霉素结合蛋白及β-内酰胺酶之间发现了两个短的氨基酸相似区域。其中一个区域包括预测的活性位点丝氨酸残基，该残基位于青霉素结合蛋白1A、1B和3序列的中间位置，在保守序列Gly-Ser-Xaa-Xaa-Lys-Pro内。另一个区域位于活性位点丝氨酸的氨基末端一侧19 - 40个残基处，可能是这些蛋白中保守的青霉素结合位点的一部分。
