SECRETION OF BETA-LACTAMASE REQUIRES THE CARBOXY END OF THE PROTEIN
SECRETION OF BETA-LACTAMASE REQUIRES THE CARBOXY END OF THE PROTEIN
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DOI：
10.1016/0092-8674(80)90321-9
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发表时间：
1980-01-01
期刊：
影响因子：
64.5
通讯作者：
BOTSTEIN, D
中科院分区：
文献类型：
--
作者：
KOSHLAND, D;BOTSTEIN, D
β的合成和分泌。研究了携带. β结构基因的P22噬菌体感染鼠伤寒沙门菌的-内酰胺酶活性。突变型或野生型的-内酰胺酶（bla基因）。野生型基因指定了2种形式的β。-内酰胺酶，其分子量相差约2500道尔顿这一差异与基于其他理由预测的23个氨基末端残基（信号序列）的去除是一致的。所有的bla突变体，包括链终止突变体，缺乏多达50%或10%的蛋白质，在这个加工步骤中显然不受影响。脉冲追踪实验表明，超过85%的野生型（和突变型）蛋白质在加工成成熟形式之前是作为完整的超长前体合成的。几乎所有成熟的野生型蛋白都出现在质周间隙，而前体的很大一部分出现在细胞质中。相比之下，β的前体和加工形式。由链终止突变体合成的-内酰胺酶蛋白（包括仅从羧基端缺少10%残基的突变体）不分泌，显然在细胞质中仍可溶解。的羧基末端氨基酸序列（至少）。-内酰胺酶是成功通过细胞质膜运输所必需的；信号序列的存在（也可能是去除的行为）显然不足以保证分泌。
Synthesis and secretion of .beta.-lactamase were studied in Salmonella typhimurium infected with P22 phage carrying the structural gene for .beta.-lactamase (the bla gene) in mutant or wild-type form. The wild-type gene specified 2 forms of .beta.-lactamase which differ in MW by about 2500 daltons. This difference is consistent with removal, predicted on other grounds, of 23 amino-terminal residues (the signal sequence). All bla- mutants, including chain-terminating mutants lacking as much as 50% or as little as 10% of the protein, were apparently unaffected in this processing step. Pulse-chase experiments showed that more than 85% of the wild-type (and mutant) proteins are synthesized as complete overlength precursors before being processed to their mature forms. Virtually all the mature wild-type protein appears in the periplasmic space, whereas a large fraction of the precursor appears in the cytoplasm. In contrast, both the precursor and processed forms of .beta.-lactamase proteins synthesized by chain-terminating mutants (including one which lacks only 10% of its residues from the carboxy end) are not secreted and apparently remain soluble in the cytoplasm. The carboxy-terminal amino acid sequence (at least) of .beta.-lactamase is essential to successful transport across the cytoplasmic membrane; the presence (and probably also the act of removal) of the signal sequence evidently does not suffice to ensure secretion.