RESUMEN
Studies on the enzymes of the cellulase complex of the thermophilic fungus Humicola grisea var. thermoidea are described. A genomic library was constructed in the phage vector EMBL 4, and from this library two clones were isolated using as a probe the cloned cbh-1 (exoglucanase, EC 3.2.1.91) gene of Phanerochaete chrysosporium, a cellulolytic basidiomycete fungus. These clones were analysed by restriction mapping and Southern blotting, and one of them (lambda 3) was sub-cloned into the M13 phage vectors mp18 and mp19. The gene sequence was determined by the dideoxy chain-termination method. Sequence comparison with the equivalent genes from P. chrysosporium and Trichoderma reesei was made: in terms of primary sequence there is about 60% homology between the three species. Secondary structure prediction of the H. grisea sequence was also computed.
Asunto(s)
Genes Fúngicos , Hongos Mitospóricos/genética , beta-Glucosidasa/genética , Secuencia de Aminoácidos , Secuencia de Bases , Southern Blotting , Clonación Molecular , Codón , ADN de Hongos , Exones , Glucano 1,3-beta-Glucosidasa , Intrones , Hongos Mitospóricos/enzimología , Datos de Secuencia Molecular , Conformación de Ácido Nucleico , Mapeo Restrictivo , Alineación de Secuencia , beta-Glucosidasa/metabolismoRESUMEN
Transcription of fungal cellulase genes may be affected by substrate induction. We studied the expression of Humicola grisea var. thermoidea cellobiohydrolase genes (cbh1.1 and cbh1.2) under induction by several soluble and insoluble carbon sources. Using the RT-PCR technique, the cbh1.2 transcript was detected in all the conditions assayed along the growth curve. Catabolite repression, which frequently occurs in other fungal celluloytic systems, was not observed. On the other hand, cbh1.1 transcription was shown to be driven by insoluble and complex lignocellulosic substrates. In summary, the cbh1.2 gene product is constitutively produced, while cbh1.1 seems to respond to a distinct regulatory mechanism.