Cloning and characterization of different domain deletion constructs of
Thermobifida fusca Cel9B
Abstract
Cel9B, an endocellulase produced by Thermobifida fusca YX, contains a
number of structural domains, including carbohydrate binding modules 2
and 4 (CBM2 and CBM4), a fibronectin-like (Fn3) domain, an Eset domain
(an Ig-like domain that may play a role in enzyme folding), a catalytic
domain, and a fibronectin-like (Fn3) domain. To elucidate the roles of
these domains with respect to Cel9B function, a series of truncation
mutants were designed and examined for their binding properties and
activities on different substrates. Different binding properties of CBM2
and 4 with a variety of substrates distinguish important roles for these
domains and provide insight as to how distinct domains interact with
each other during substrate degradation. The results of this study
implicate the collective roles of the non-catalytic domains with respect
to Cel9B function, and in turn, this information can be incorporated
into protein engineering strategies for improved biomass conversion.