Identification and characterization of a gene and protein required for glycosylation in the yeast Golgi.
The MNN2 gene of Saccharomyces cerevisiae has been cloned by complementation of the mnn2 mutant phenotype scored by a change in cell surface carbohydrate structure resulting from a lack of alpha 1----2-mannose branching in the outer chain. The gene was subcloned as a 3 kb DNA fragment that integrated at the MNN2 locus, and a gene disruption yielded the mnn2 phenotype. A lacZ-MNN2 gene fusion protein, produced in Escherichia coli, was used to raise a specific antiserum that recognized a 65 kD wild-type yeast protein. This MNN2 gene product lacks N-linked carbohydrate but appears to be an integral membrane protein. Overproduction of MNN2p does not enhance the alpha 1----2-mannosyltransferase activity of yeast cells. The results suggest that MNN2p is a Golgi-associated protein that is involved in mannoprotein sorting rather than glycosylation.
Devlin
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Department of Biochemistry, University of California, Berkeley 94720.
Ballou
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D003001:Cloning, Molecular; D004271:DNA, Fungal / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D005800:Genes, Fungal; D005816:Genetic Complementation Test; D005838:Genotype; D006031:Glycosylation; D006056:Golgi Apparatus / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000378:metabolism; D009693:Nucleic Acid Hybridization; D010957:Plasmids; D011499:Protein Processing, Post-Translational; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D013104:Spheroplasts / Q000378:metabolism
D004271:DNA, Fungal; D005656:Fungal Proteins; D008562:Membrane Glycoproteins; C025363:mannoproteins