title: Characterization of two allelic forms of Neurospora crassa laccase. Amino- and carboxyl-terminal processing of a precursor.
abstract: The complete structures of the laccase genes isolated from two different Neurospora crassa wild-type strains are described. The genes were cloned by screening partial genomic DNA libraries with a nick-translated laccase-specified 1.36-kilobase SalI fragment (Germann, U. A., and Lerch, K. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 8854-8858) as a hybridization probe. Nucleotide sequence analysis revealed the presence of two different allelic forms. They conform to the same structural organization, but show an overall divergence of 5.3% which is mainly the result of point mutations in the nontranslated regions. The coding parts are interrupted by a short intron. The encoded proteins differ in 12 out of 619 amino acid residues. A comparison of the primary structure deduced from the nucleotide sequence of the gene with a protein chemical analysis of the two terminal cyanogen bromide fragments of extracellular N. crassa laccase revealed that the enzyme is synthesized as a precursor. The precursor protein exceeds the mature protein by 49 amino acids at its amino terminus and by 13 amino acids at its carboxyl terminus, thus indicating a complex maturation pathway. The possible involvement of amino-terminal processing in secretion and of carboxyl-terminal processing in activation of the enzyme is discussed.
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D004792:Enzyme Precursors / Q000235:genetics*; D007527:Isoenzymes / Q000235:genetics; D042845:Laccase; D008969:Molecular Sequence Data; D009491:Neurospora / Q000201:enzymology*; D009492:Neurospora crassa / Q000201:enzymology* / Q000235:genetics; D010088:Oxidoreductases / Q000235:genetics*; D011110:Polymorphism, Genetic
chemical_list: D004792:Enzyme Precursors; D007527:Isoenzymes; D010088:Oxidoreductases; D042845:Laccase