A new enzyme superfamily - The phosphopantetheinyl transferases
A new enzyme superfamily - The phosphopantetheinyl transferases
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DOI：
10.1016/s1074-5521(96)90181-7
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发表时间：
1996-11-01
影响因子：
--
通讯作者：
Walsh, CT
中科院分区：
文献类型：
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作者：
Lambalot, RH;Gehring, AM;Walsh, CT
背景：所有的聚酮合成酶、脂肪酸合成酶和非核糖体多肽合成酶都需要对其组成的酰基载体蛋白结构域(S)进行翻译后修饰才能具有催化活性。通过将辅酶A的4‘-磷酸丙氨酸(P-PANT)部分翻译后转移到每个酰基载体蛋白结构域中保守的丝氨酸残基的侧链羟基上，非活性的脱辅基蛋白被转化为活性的空洞形式。第一个被克隆和鉴定的P-PANT转移酶是最近报道的大肠杆菌ACPS酶，它负责脂肪酸合成酶从APE到HOLE的转化。令人惊讶的是，对序列数据库的初步搜索没有发现任何与ACPS有显著相似性的蛋白质。结果：通过与ACPS肽序列低水平相似性的序列比对，我们鉴定了几个潜在的ACPS同源物之间共享的两个共同基序。这导致了一个与ACPS有12-22%相似性的蛋白质大家族的鉴定，这些蛋白质是推定的P-PANT转移酶。这些蛋白中的三个，E.coliEntD和O195，以及B.subtilis SFP，已经被大量生产和纯化，并被发现具有P-PANT转移酶活性，证实了观察到的低水平的序列同源性正确地预测了催化功能。目前已知在大肠杆菌中存在三种P-PANT转移酶(ACPS、EntD和o195)；ACPS和EntD分别专用于激活脂肪酸合成酶和肠动蛋白合成酶。O195的类人猿蛋白底物尚未确定。结论：ACPS和EntD对不同的P-PANT要求酶的特异性表明，每个P-PANT要求合酶都有自己的伙伴酶负责其酰基载体结构域的apo到Hole的激活。这是第一个直接证据表明，在包含多个P-PANT需要途径的生物体中，每个途径都有自己的翻译后修饰活性。
Background: All polyketide synthases, fatty acid synthases, and non-ribosomal peptide synthetases require posttranslational modification of their constituent acyl carrier protein domain(s) to become catalytically active. The inactive apoproteins are converted to their active hole-forms by posttranslational transfer of the 4'-phosphopantetheinyl (P-pant) moiety of coenzyme A to the sidechain hydroxyl of a conserved serine residue in each acyl carrier protein domain. The first P-pant transferase to be cloned and characterized was the recently reported Escherichia coli enzyme ACPS, responsible for ape to hole conversion of fatty acid synthase. Surprisingly, initial searches of sequence databases did not reveal any proteins with significant peptide sequence similarity with ACPS.Results: Through refinement of sequence alignments that indicated low level similarity with the ACPS peptide sequence, we identified two consensus motifs shared among several potential ACPS homologs. This has led to the identification of a large family of proteins having 12-22% similarity with ACPS, which are putative P-pant transferases. Three of these proteins, E. coli EntD and o195, and B. subtilis Sfp, have been overproduced, purified and found to have P-pant transferase activity, confirming that the observed low level of sequence homology correctly predicted catalytic function. Three P-pant transferases are now known to be present in E. coli (ACPS, EntD and o195); ACPS and EntD are specific for the activation of fatty acid synthase and enterobactin synthetase, respectively. The ape-protein substrate for o195 has not yet been identified. Sfp is responsible for the activation of the surfactin synthetase.Conclusions: The specificity of ACPS and EntD for distinct P-pant-requiring enzymes suggests that each P-pant-requiring synthase has its own partner enzyme responsible for apo to hole activation of its acyl carrier domains. This is the first direct evidence that in organisms containing multiple P-pant-requiring pathways, each pathway has its own posttranslational modifying activity.