New potential cell wall glucanases of Saccharomyces cerevisiae and their involvement in mating.

Biotinylation of intact Saccharomyces cerevisiae cells with a nonpermeant reagent (Sulfo-NHS-LC-Biotin) allowed the identification of seven cell wall proteins that were released from intact cells by dithiothreitol (DTT). By N-terminal sequencing, three of these proteins were identified as the known proteins beta-exoglucanase 1 (Exg1p), beta-endoglucanase (Bgl2p), and chitinase (Cts1p). One protein was related to the PIR protein family, whereas the remaining three (Scw3p, Scw4p, and Scw10p [for soluble cell wall proteins]) were found to be related to glucanases. Single knockouts of these three potential glucanases did not result in dramatic phenotypes. The double knockout of SCW4 and the homologous gene SCW10 resulted in slower growth, significantly increased release of proteins from intact cells by DTT, and highly decreased mating efficiency when these two genes were disrupted in both mating types. The synergistic behavior of the disruption of SCW4 and SCW10 was partly antagonized by the disruption of BGL2. The data are discussed in terms of a possible counterplay of transglucosidase and glucosidase activities.

Histological aspects of the stomach (proventriculus and gizzard) of the red-capped cardinal (paroaria gularis gularis, Linnaeus, 1766)

Un estudio morfológico (histológico) del estómago (proventrículo y molleja) del cardenal rojo (Paroaria gularis gularis) fue efectuado bajo microscopio de luz. Anatómicamente, el estómago del cardenal rojo está constituido por dos cámaras distintas; la región craneal, glandular o el proventrículo (proventriculus, pars glandularis), la cual se está conectada cranialmente con el esófago y caudalmente, está el ventrículo (ventriculos, pars muscularis) también conocida como porción muscular. Ambas, la túnica mucosa del proventrículo y del ventrículo presentan pliegues alineados de epitelio simple prismático. Una cutícula densa está colocada encima de la túnica mucosa del ventrículo. En la lámina propia de ambas regiones, se encuentran glándulas tubulares simples. La submucosa del proventrículo está ocupado por glándulas proventriculares profundas. Debido a la ausencia de una mucosa muscular, la submucsa del ventrículo no puede ser distinguido de la lámina propia. La túnica mucosa del proventrículo, consiste de un lecho interior longitudinal, de un lecho intermedio circular y de un lecho externo longitudinal discontinuo de músculo liso. En el ventrículo, consiste de un lecho longitudinal interno y de un lecho circular externo. Em ambas cámaras, la serosa está constituida por tejido conectivo revestido por mesotelio, conteniendo vasos sanguíneos, elementos nerviosos del plexo seroso y tejido adiposo

Mating type-specific cell-cell recognition of Saccharomyces cerevisiae: cell wall attachment and active sites of a- and alpha-agglutinin.

Mating type-specific agglutination of Saccharomyces cerevisiae a and alpha cells depends on the heterophilic interaction of two cell surface glycoproteins, the gene products of AG alpha 1 and AGA2. Evidence is presented with immunogold labelling that the alpha-agglutinin is part of the outer fimbrial cell wall coat. The a-agglutinin is bound via two S-S bridges (Cys7 and Cys50) to a cell wall component, most probably the gene product of AGA1. His273 of alpha-agglutinin has previously been shown to be essential for a- and alpha-agglutinin interaction and a model based on two opposing ion-pairs had been proposed. By site-directed mutagenesis this possibility has now been excluded. With the help of various peptides, either chemically synthesized, obtained by proteolysis of intact glycosylated a-agglutinin or prepared from a fusion protein expressed in Escherichia coli, the biologically active region of a-agglutinin was located at the C-terminus of the molecule. A peptide consisting of the C-terminal 10 amino acids (GSPIN-TQYVF) was active in nanomolar concentrations. Saccharide moieties, therefore, are not essential for the mating type-specific cell-cell interaction; glycosylated peptides are, however, four to five times more active than non-glycosylated ones. Comparisons of the recognition sequences of the S. cerevisiae agglutinins with that of the Dictyostelium contact site A glycoprotein (gp80), as well as with those of the various families of cell adhesion molecules of higher eucaryotes, have been made and are discussed.

Saccharomyces cerevisiae a- and alpha-agglutinin: characterization of their molecular interaction.

An O-glycosylated protein of approximately 18 kDa responsible for mating type specific agglutination has been isolated from Saccharomyces cerevisiae a cells, purified to homogeneity and via peptide sequences the gene was cloned by PCR. An open reading frame codes for a protein of 69 amino acids. A minimum of five serine and five threonine residues of the mature protein are glycosylated. alpha-Agglutinin is a highly N-glycosylated protein of approximately 250 kDa. Both purified agglutinins form a specific 1:1 complex in vitro. Pretreatment of alpha-agglutinin, but not of alpha-agglutinin, with diethylpyrocarbonate (DEPC) prevents formation of the complex; treatment of alpha-agglutinin in the presence of alpha-agglutinin protects the former from DEPC inactivation. By carboxy terminal shortening of the alpha-agglutinin gene and by replacing three of its eight histidyl residues by arginine, the active region of alpha-agglutinin for interaction with alpha-agglutinin has been defined. Neither the N- nor the O-linked saccharides of the two agglutinins seem to be essential for their interaction.