title: Unexpected homology between inducible cell wall protein QID74 of filamentous fungi and BR3 salivary protein of the insect Chironomus.
abstract: A gene, qid74, of mycoparasitic filamentous fungus Trichoderma harzianum and its allies encodes a cell wall protein that is induced by replacing glucose in the culture medium with chitin (simulated mycoparasitism conditions). Because no trace of this gene can be detected in related species such as Gibberella fujikuroi and Saccharomyces cerevisiae, the qid74 gene appears to have arisen de novo within the genus Trichoderma. Qid74 protein, 687 residues long, is now seen as highly conserved tandem repeats of the 59-residue-long unit. This unit itself, however, may have arisen as tandem repeats of the shorter 13-residue-long basic unit. Within the genus Trichoderma, the amino acid sequence of Qid74 proteins has been conserved in toto. The most striking is the fact that Qid74 shares 25.3% sequence identity with the carboxyl-terminal half of the 1,572-residue-long BR3 protein of the dipteran insect Chironomus tentans. BR3 protein is secreted by the salivary gland of each aquatic larva of Chironomus to form a tube to house itself. Furthermore, the consensus sequence derived from these 59-residue-long repeating units resembles those of epidermal growth factor-like domains found in divergent invertebrate and vertebrate proteins as to the positions of critical cysteine residues and homology of residues surrounding these cysteines.
authors.affiliation: Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Apartado, 1095 Sevilla, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Rey
authors.forename: S
authors.initials: S
authors.lastname: Ohno
authors.forename: J A
authors.initials: JA
authors.lastname: Pintor-Toro
authors.forename: A
authors.initials: A
authors.lastname: Llobell
authors.forename: T
authors.initials: T
authors.lastname: Benitez
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002683:Chironomidae / Q000235:genetics* / Q000378:metabolism; D019143:Evolution, Molecular; D005656:Fungal Proteins / Q000235:genetics*; D019476:Insect Proteins / Q000235:genetics*; D008565:Membrane Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D012471:Salivary Proteins and Peptides / Q000235:genetics*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: C112569:BR3 protein, Chironomus tentans; D005656:Fungal Proteins; D019476:Insect Proteins; D008565:Membrane Proteins; C112570:QID74 protein, Trichoderma harzianum; D012471:Salivary Proteins and Peptides