The Structure of a Bacterial Cellobiohydrolase: The Catalytic Core of the Thermobifida fusca Family GH6 Cellobiohydrolase Cel6B

Sandgren, MatsSwedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för molekylärbiologi,Department of Molecular Biology (författare)

The Structure of a Bacterial Cellobiohydrolase : The Catalytic Core of the Thermobifida fusca Family GH6 Cellobiohydrolase Cel6B

Cellulases, glycoside hydrolases that catalyze the degradation of cellulose, are classified as either endoglucanases or cellobiohydrolases (CBHs) based on their architecture and mode of action on the cellulose. CBHs bind the cellulose chain in a more or less closed tunnel and cleave off cellobiose units processively from one end of the cellulosic polymer, while endoglucanases have their active sites in a more or less open cleft and show a higher tendency to cut bonds internally in the polymer. The CBH Cel6A (also called CBH2) from the ascomycete Hypocrea jecorina has a much shorter substrate-binding tunnel and seems less processive than the CBH Cel7A (CBH1), from the same fungus. Here, we present the X-ray crystal structure of the catalytic domain of the CBH Cel6B, also called E3, from the soil bacterium Thermobifida fusca, both in its apo form and co-crystallized with cellobiose. The enzyme structure reveals that the Cel6B enzyme has a much longer substrate-binding site than its fungal GH6 counterparts. The tunnel is comparable in length to that of GH7 CBHs. In the ligand structure with cellobiose, the tunnel exit is completely closed by a 13-residue loop not present in fungal GH6 enzymes. The loop needs to be displaced to allow cellobiose product release for a processive action by the enzyme. When ligand is absent, seven of these residues are not visible in the electron density and the tunnel exit is open.

Wu, MiaoSwedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för molekylärbiologi,Department of Molecular Biology(Swepub:slu)47475 (författare)
Karkehabadi, SaeidSwedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för molekylärbiologi,Department of Molecular Biology(Swepub:slu)50359 (författare)
Mitchinson, ColinDuPont Ind Biosci, Palo Alto, CA 94304 USA. (författare)
Kelemen, Bradley R.DuPont Ind Biosci, Palo Alto, CA 94304 USA. (författare)
Larenas, Edmundo A.DuPont Ind Biosci, Palo Alto, CA 94304 USA. (författare)
Ståhlberg, JerrySwedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för molekylärbiologi,Department of Molecular Biology(Swepub:slu)50155 (författare)
Hansson, HenrikSwedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för molekylärbiologi,Department of Molecular Biology(Swepub:slu)46677 (författare)
Sveriges lantbruksuniversitetInstitutionen för molekylärbiologi (creator_code:org_t)
Sveriges lantbruksuniversitet

Ingår i:Journal of Molecular Biology: Elsevier BV425:3, s. 622-6350022-28361089-8638

Av författaren/redakt...: Sandgren, Mats; Wu, Miao; Karkehabadi, Sae ...; Mitchinson, Coli ...; Kelemen, Bradley ...; Larenas, Edmundo ...; visa fler...; Ståhlberg, Jerry; Hansson, Henrik; visa färre...

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