Expression, crystal structure and cellulase activity of the thermostable cellobiohydrolase Cel7A from the fungus Humicola grisea var. thermoidea

Majid Haddad Momeni, Frits Goedegebuur, Henrik Hansson, Saeid Karkehabadi, Glareh Askarieh, Colin Mitchinson, Edmundo A. Larenas, Jerry Ståhlberg, Mats Sandgren

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Glycoside hydrolase family 7 (GH7) cellobiohydrolases (CBHs) play a key role in biomass recycling in nature. They are typically the most abundant enzymes expressed by potent cellulolytic fungi, and are also responsible for the majority of hydrolytic potential in enzyme cocktails for industrial processing of plant biomass. The thermostability of the enzyme is an important parameter for industrial utilization. In this study, Cel7 enzymes from different fungi were expressed in a fungal host and assayed for thermostability, including Hypocrea jecorina Cel7A as a reference. The most stable of the homologues, Humicola grisea var. thermoidea Cel7A, exhibits a 10ºC higher melting temperature (Tm of 72.5ºC) and showed a 4-5 times higher initial hydrolysis rate than H. jecorina Cel7A on phosphoric acid-swollen cellulose and showed the best performance of the tested enzymes on pretreated corn stover at elevated temperature (65ºC, 24 h). The enzyme shares 57% sequence identity with H. jecorina Cel7A and consists of a GH7 catalytic module connected by a linker to a C-terminal CBM1 carbohydrate-binding module. The crystal structure of the H. grisea var. thermoidea Cel7A catalytic module (1.8 angstrom resolution; Rwork and Rfree of 0.16 and 0.21, respectively) is similar to those of other GH7 CBHs. The deviations of several loops along the cellulose-binding path between the two molecules in the asymmetric unit indicate higher flexibility than in the less thermostable H. jecorina Cel7A.
Original languageEnglish
JournalActa Crystallographica. Section D: Biological Crystallography
Volume70
Issue numberPt 9
Pages (from-to)2356-2366
Number of pages11
ISSN0907-4449
DOIs
Publication statusPublished - 2014
Externally publishedYes

Keywords

  • Cellobiohydrolase
  • Cel7A

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