Substrate specificity of the SecB chaperone
Substrate specificity of the SecB chaperone
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DOI：
10.1074/jbc.274.48.34219
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发表时间：
1999-11-26
影响因子：
4.8
通讯作者：
Bukau, B
中科院分区：
文献类型：
--
作者：
Knoblauch, NTM;Rüdiger, S;Bukau, B
细菌分子伴侣SecB协助蛋白质穿过内膜移位。其区分分泌蛋白和胞质蛋白的机制知之甚少。为了鉴定其结合基序，我们筛选了2688个肽，覆盖SecB结合的23种蛋白质的序列。基序类似于9个残基长，富含芳香族和碱性残基，而酸性残基是不利的。它的识别允许预测蛋白质序列内的结合区域，准确率高达87%。SecB结合区在统计学上每20-30个残基出现一次。在SecB依赖性和非依赖性分泌蛋白和胞质蛋白中，结合区域的发生和亲和力是相似的，并且SecB对信号序列缺乏特异性。因此SecB不能通过其结合特异性区分分泌和非分泌蛋白。这一结论得到SecB结合变性荧光素酶，从而允许随后通过DnaK系统重折叠的发现的支持。SecB可能是一个一般的伴侣蛋白，其参与易位是由SecB和SecB结合的前蛋白的信号序列与易位装置的相互作用介导的。
The bacterial chaperone SecB assists translocation of proteins across the inner membrane. The mechanism by which it differentiates between secretory and cytosolic proteins is poorly understood. To identify its binding motif, we screened 2688 peptides covering sequences of 23 proteins for SecB binding. The motif is similar to 9 residues long and is enriched in aromatic and basic residues, whereas acidic residues are disfavored. Its identification allows the prediction of binding regions within protein sequences with up to 87% accuracy. SecB-binding regions occur statistically every 20-30 residues. The occurrence and affinity of binding regions are similar in SecB-dependent and -independent secretory proteins and in cytosolic proteins, and SecB lacks specificity toward signal sequences. SecB cannot thus differentiate between secretory and non-secretory proteins via its binding specificity. This conclusion is supported by the finding that SecB binds denatured luciferase, thereby allowing subsequent refolding by the DnaK system. SecB may rather be a general chaperone whose involvement in translocation is mediated by interactions of SecB and signal sequences of SecB-bound preproteins with the translocation apparatus.