Raghothama S, Eberhardt R Y, Simpson P, Wigelsworth D, White P, Hazlewood G P, Nagy T, Gilbert H J, Williamson M P
Department of Molecular Biology and Biotechnology, Krebs Institute, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
Nat Struct Biol. 2001 Sep;8(9):775-8. doi: 10.1038/nsb0901-775.
The recycling of photosynthetically fixed carbon in plant cell walls is a key microbial process. In anaerobes, the degradation is carried out by a high molecular weight multifunctional complex termed the cellulosome. This consists of a number of independent enzyme components, each of which contains a conserved dockerin domain, which functions to bind the enzyme to a cohesin domain within the protein scaffoldin protein. Here we describe the first three-dimensional structure of a fungal dockerin, the N-terminal dockerin of Cel45A from the anaerobic fungus Piromyces equi. The structure contains a novel fold of 42 residues. The ligand binding site consists of residues Trp 35, Tyr 8 and Asp 23, which are conserved in all fungal dockerins. The binding site is on the opposite side of the N- and C-termini of the molecule, implying that tandem dockerin domains, seen in the majority of anaerobic fungal plant cell wall degrading enzymes, could present multiple simultaneous binding sites and, therefore, permit tailoring of binding to catalytic demands.
植物细胞壁中光合固定碳的循环是一个关键的微生物过程。在厌氧菌中，降解是由一种称为纤维小体的高分子量多功能复合物进行的。它由许多独立的酶组分组成，每个酶组分都含有一个保守的dockerin结构域，其功能是将酶与蛋白质支架蛋白中的黏连蛋白结构域结合。在此，我们描述了一种真菌dockerin的首个三维结构，即来自厌氧真菌埃氏梨形孢（Piromyces equi）的Cel45A的N端dockerin。该结构包含一个由42个残基组成的新型折叠。配体结合位点由Trp 35、Tyr 8和Asp 23残基组成，这些残基在所有真菌dockerin中都是保守的。结合位点位于分子N端和C端的相对侧，这意味着在大多数厌氧真菌植物细胞壁降解酶中看到的串联dockerin结构域可以呈现多个同时存在的结合位点，因此能够根据催化需求定制结合。
