Two new cellulose-growth specific () cDNAs, and , have been isolated from an cDNA expression library by immunoscreening with an anti-‘endoglucanase’ antibody. The deduced amino acid sequences showed that both CEL2 and CEL4 proteins have a modular structure consisting of a fungal-type cellulose-binding domain (CBD) and a catalytic domain separated by a linker region rich in Pro, Ser and Thr. The CEL2 and CEL4 catalytic domains were homologous to fungal cellobiohydrolases (CBH) in family 7 and to fungal mannanases in family 5 of the glycosyl hydrolases, respectively. A previously isolated cDNA derived from a constitutive gene was also sequenced. The deduced amino acid sequence corresponded to 5-aminolaevulinic acid synthase (ALA), the first enzyme in the haem biosynthetic pathway, and was most similar to other fungal ALAs. RNA analysis showed that the expression of and genes was induced by cellulose and repressed by glucose, fructose and lactose. The soluble cellulose derivative CM-cellulose induced mRNA accumulation for but not or Mannitol, maltose, sorbitol and glycerol decreased and mRNA levels to different extents, and mRNAs all disappeared after the addition of glucose with apparent half-lives of less than 20 min. Whether mRNAs have short half-lives or glucose affects the stability of transcripts remains to be investigated.


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