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首页> 外文期刊>Biochemistry >STRUCTURAL ROLE OF CALCIUM FOR THE ORGANIZATION OF THE CELLULOSOME OF CLOSTRIDIUM THERMOCELLUM
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STRUCTURAL ROLE OF CALCIUM FOR THE ORGANIZATION OF THE CELLULOSOME OF CLOSTRIDIUM THERMOCELLUM

机译：钙的结构作用在嗜热梭状芽胞杆菌的细胞质中

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The cellulosome of Clostridium thermocellum is a multipolypeptide complex of structural and catalytic subunits. Several of the catalytic subunits have at the carboxyl end a conserved duplicated region (CDR) which interacts with internally repeated elements (IREs) of scaffolding subunits such as CipA. This interaction requires calcium. The two parts of the CDR region here designated CDR1 and CDR2 (closest to the carboxyl end) each consist of about 20 amino acid residues. As shown in our previous paper [Choi, S. K., & Ljungdahl, L. G. (1996) Biochemistry 35, 4897-4905], treatment of the cellulosome with ethylenediaminetetraacetic acid (EDTA) under aerobic conditions disintegrates the cellulosome with formation of truncated catalytic subunits. The cleavage is at a specific asparagine residue located within CDR1 and occurs with complete loss of CDR2. Two branched peptides containing the amino acid sequences of CDR1 and CDR2 (designated bCDR1 and bCDR2) were synthesized, and specific antibodies were raised against them. These antibodies did not cross react with bCDR1 or bCDR2, respectively. After sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting, it was observed that about 15 subunits of the cellulosome reacted with anti-bCDR1 and anti-bCDR2. In a similar experiment with EDTA-treated cellulosomes, these subunits reacted with anti-bCDR1 but not with anti-bCDR2, showing that they lost the bCDR2 epitope and were truncated. The peptide bCDR1 binds calcium, whereas bCDR2 does not. Furthermore, bCDR1 but not bCDR2. binds to CipA, presumably at IRE regions. This binding requires calcium. A model is proposed for the binding of the catalytic subunits to CipA which involves CDR1, an IRE, and calcium.
机译：热纤梭菌的纤维素体是结构和催化亚基的多肽复合物。几个催化亚基在羧基端具有一个保守的重复区域（CDR），该区域与支架亚基（例如CipA）的内部重复元件（IREs）相互作用。这种相互作用需要钙。 CDR区的两个部分，此处称为CDR1和CDR2（最靠近羧基端），每个部分都包含约20个氨基酸残基。如我们先前的论文[Choi，S.K。，＆Ljungdahl，L.G。（1996）Biochemistry 35，4897-4905]中所示，在有氧条件下用乙二胺四乙酸（EDTA）处理纤维素体会分解纤维素体，形成截短的催化亚基。切割在位于CDR1内的特定天冬酰胺残基处，并在CDR2完全丢失的情况下发生。合成了两个包含CDR1和CDR2氨基酸序列的分支肽（称为bCDR1和bCDR2），并针对它们产生了特异性抗体。这些抗体不会分别与bCDR1或bCDR2交叉反应。在十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（SDS-PAGE）和Western印迹后，观察到约15个亚单位的纤维素体与抗bCDR1和抗bCDR2反应。在用EDTA处理的纤维素体的类似实验中，这些亚基与抗bCDR1反应，但不与抗bCDR2反应，表明它们失去了bCDR2表位并被截短。肽bCDR1结合钙，而bCDR2不结合钙。此外，bCDR1但不是bCDR2。可能在IRE区与CipA结合。这种结合需要钙。提出了用于催化亚基与CipA结合的模型，该模型涉及CDR1，IRE和钙。

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