Crh1p and Crh2p are required for the cross-linking of chitin to beta(1-6)glucan in the Saccharomyces cerevisiae cell wall.
In budding yeast, chitin is found in three locations: at the primary septum, largely in free form, at the mother-bud neck, partially linked to beta(1-3)glucan, and in the lateral wall, attached in part to beta(1-6)glucan. By using a recently developed strategy for the study of cell wall cross-links, we have found that chitin linked to beta(1-6)glucan is diminished in mutants of the CRH1 or the CRH2/UTR2 gene and completely absent in a double mutant. This indicates that Crh1p and Crh2p, homologues of glycosyltransferases, ferry chitin chains from chitin synthase III to beta(1-6)glucan. Deletion of CRH1 and/or CRH2 aggravated the defects of fks1Delta and gas1Delta mutants, which are impaired in cell wall synthesis. A temperature shift from 30 degrees C to 38 degrees C increased the proportion of chitin attached to beta(1-6)glucan. The expression of CRH1, but not that of CRH2, was also higher at 38 degrees C in a manner dependent on the cell integrity pathway. Furthermore, the localization of both Crh1p and Crh2p at the cell cortex, the area where the chitin-beta(1-6)glucan complex is found, was greatly enhanced at 38 degrees C. Crh1p and Crh2p are the first proteins directly implicated in the formation of cross-links between cell wall components in fungi.
Cabib
Enrico
E
National Institute of Diabetes and Digestive and Kidney Diseases, Laboratory of Biochemistry and Genetics, Bethesda, MD 20892, USA. enricoc@bdg10.niddk.nih.gov
Blanco
Noelia
N
Grau
Cecilia
C
Rodríguez-Peña
José Manuel
JM
Arroyo
Javier
J
D002473:Cell Wall / Q000737:chemistry / Q000378:metabolism*; D002686:Chitin / Q000378:metabolism*; D006026:Glycoside Hydrolases / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D013696:Temperature; D047071:beta-Glucans / Q000378:metabolism*
D029701:Saccharomyces cerevisiae Proteins; D047071:beta-Glucans; D002686:Chitin; C407735:CRH1 protein, S cerevisiae; D006026:Glycoside Hydrolases; C407734:UTR2 protein, S cerevisiae