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Vol 46(2012) N 6 p. 817-822; I.A. Dvortsov1*, N.A. Lunina1, V.V. Zverlov1,2, G.A. Velikodvorskaya1 Properties of Four C-Terminal Carbohydrate-Binding Modules (CBM4) of Laminarinase Lic16A of Clostridium thermocellum 1Institute of Molecular genetics, Russian Academy of Sciences, Moscow, 123182 Russia2Department of Microbiology, Technische Universität München, Freising, 85350, Germany *dvortsov@img.ras.ru Received - 2012-04-11; Accepted - 2012-04-27 At the C-terminus of multimodular laminarinase Lic16A from Clostridium thermocellum, four carbohydrate-binding modules (CBM) of family 4 were found. Isolated CBM4_1, CBM4_2, CBM4_3, and CBM4_4 modules and the CBM4_(1-4) tandem were obtained. None of the recombinant proteins had the affinity to soluble β-1,3-1,4-glucans, laminarin and lichenan, the main specific Lic16A substrates. All modules, except CBM4_4, had the ability to bind bacterial crystalline cellulose, which is atypical of family-4 CBMs. All CBMs 4 of Lic16A had an affinity to xylan, chitin, yeast cell wall β-glucan, and avicel, while CBM4_3 and CBM4_4 also had an affinity to chitosan. The CBM4_(1-4) tandem had the highest affinity to the β-glucan, avicel, and pustulan of the yeast cell wall. The CBM4_(1-4) binding constants for these substrates were approximately 100-fold higher than those of its individual modules, which suggests synergy in the process of absorbing these polysaccharides. This finding helps to explain the evolutionary process of CBM multiplication. Clostridium thermocellum, laminarinase, multimodular proteins, carbohydrate binding modules, β-glucan, binding sites, synergy |
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