In:
The FEBS Journal, Wiley, Vol. 282, No. 23 ( 2015-12), p. 4515-4537
Abstract:
The ascomycete Geotrichum candidum is a versatile and efficient decay fungus that is involved, for example, in biodeterioration of compact discs; notably, the 3C strain was previously shown to degrade filter paper and cotton more efficiently than several industrial enzyme preparations. Glycoside hydrolase ( GH ) family 7 cellobiohydrolases ( CBH s) are the primary constituents of industrial cellulase cocktails employed in biomass conversion, and feature tunnel‐enclosed active sites that enable processive hydrolytic cleavage of cellulose chains. Understanding the structure–function relationships defining the activity and stability of GH 7 CBH s is thus of keen interest. Accordingly, we report the comprehensive characterization of the GH 7 CBH secreted by G. candidum ( Gca Cel7A). The bimodular cellulase consists of a family 1 cellulose‐binding module ( CBM ) and linker connected to a GH 7 catalytic domain that shares 64% sequence identity with the archetypal industrial GH 7 CBH of Hypocrea jecorina ( Hje Cel7A). Gca Cel7A shows activity on Avicel cellulose similar to Hje Cel7A, with less product inhibition, but has a lower temperature optimum (50 °C versus 60–65 °C, respectively). Five crystal structures, with and without bound thio‐oligosaccharides, show conformational diversity of tunnel‐enclosing loops, including a form with partial tunnel collapse at subsite –4 not reported previously in GH 7. Also, the first O‐ glycosylation site in a GH 7 crystal structure is reported – on a loop where the glycan probably influences loop contacts across the active site and interactions with the cellulose surface. The Gca Cel7A structures indicate higher loop flexibility than Hje Cel7A, in accordance with sequence modifications. However, Gca Cel7A retains small fluctuations in molecular simulations, suggesting high processivity and low endo‐initiation probability, similar to Hje Cel7A. Database Structural data are available in the Protein Data Bank under the accession numbers 5AMP , 4ZZV , 4ZZW , 4ZZT , and 4ZZU . The Geotrichum candidum GH family 7 cellobiohydrolase nucleotide sequence is available in GenBank under accession number KJ958925 . Enzymes Glycoside hydrolase family 7 reducing end acting cellobiohydrolase
Type of Medium:
Online Resource
ISSN:
1742-464X
,
1742-4658
DOI:
10.1111/febs.2015.282.issue-23
Language:
English
Publisher:
Wiley
Publication Date:
2015
detail.hit.zdb_id:
2172518-4
SSG:
12
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