Lucana Darío Ortiz de Orué, Schaa Tanja, Schrempf Hildgund
Universität Osnabrück, FB Biologie/Chemie, Barbarastraße 11, D-49069 Osnabrück, Germany.
Microbiology (Reading). 2004 Aug;150(Pt 8):2575-2585. doi: 10.1099/mic.0.27091-0.
The Gram-positive soil bacterium and cellulose degrader Streptomyces reticuli synthesizes the mycelium-associated enzyme CpeB, which displays haem-dependent catalase and peroxidase activity, as well as haem-independent manganese-peroxidase activity. Downstream of the cpeB gene, a so far unknown gene was identified. The new gene and its mutated derivatives were cloned in Escherichia coli as well as in Streptomyces lividans and a gene-disruption mutant within the chromosome of the original S. reticuli host was constructed, comparative physiological, biochemical and immunological studies then allowed the deduction of the following characteristics of the novel gene product. (i) The protein was found extracellularly; the substitution of twin arginines within the signal peptide abolished its secretion. (ii) The highly purified protein interacted specifically with haem and hence was designated HbpS (haem-binding protein of Streptomyces). (iii) HbpS contained three histidine residues surrounded by hydrophobic amino acids; one of them was located within the motif LX(3)THLX(10)AA, which is related to the motif within the yeast cytochrome c peroxidase LX(2)THLX(10)AA whose histidine residue interacts with haem. (iv) The addition of haemin (Fe(3+) oxidized form of haem) to the Streptomyces cultures led to enhanced levels of HbpS which correlated with increased haemin-resistance. (v) The presence of HbpS increased synthesis of the highly active catalase-peroxidase CpeB containing haem. In this process HbpS could act as a chaperone that binds haem and then delivers it to the mycelium-associated CpeB; HbpS could also interact with membrane-associated proteins involved in a signal transduction cascade regulating the expression of cpeB. (vi) HbpS shared varying degrees of amino acid identities with bacterial proteins of so far unknown function. This report contributes to the elucidation of the biological function of these proteins.
革兰氏阳性土壤细菌兼纤维素降解菌网状链霉菌合成了与菌丝体相关的酶CpeB，该酶具有依赖血红素的过氧化氢酶和过氧化物酶活性，以及不依赖血红素的锰过氧化物酶活性。在cpeB基因的下游，鉴定出一个迄今未知的基因。该新基因及其突变衍生物被克隆到大肠杆菌和变铅青链霉菌中，并构建了原始网状链霉菌宿主染色体中的基因破坏突变体，随后通过比较生理、生化和免疫学研究推断出该新基因产物的以下特征。(i) 该蛋白质在细胞外被发现；信号肽内双精氨酸的替换消除了其分泌。(ii) 高度纯化的蛋白质与血红素特异性相互作用，因此被命名为HbpS（链霉菌血红素结合蛋白）。(iii) HbpS包含三个被疏水氨基酸包围的组氨酸残基；其中一个位于基序LX(3)THLX(10)AA内，该基序与酵母细胞色素c过氧化物酶LX(2)THLX(10)AA内的基序相关，其组氨酸残基与血红素相互作用。(iv) 向链霉菌培养物中添加血红素（血红素的Fe(3+)氧化形式）导致HbpS水平升高，这与血红素抗性增加相关。(v) HbpS的存在增加了含血红素的高活性过氧化氢酶-过氧化物酶CpeB的合成。在此过程中，HbpS可以作为伴侣蛋白，结合血红素然后将其传递给与菌丝体相关的CpeB；HbpS还可以与参与调节cpeB表达的信号转导级联的膜相关蛋白相互作用。(vi) HbpS与迄今功能未知的细菌蛋白具有不同程度的氨基酸同一性。本报告有助于阐明这些蛋白质的生物学功能。
