MCB 2050 Lecture Notes - Lecture 8: Protein Folding, Calnexin, Proteasome

• School: University of Guelph
• Department: Molecular and Cellular Biology
• Course: MCB 2050
• Professor: Peter Krell

Document Summary

During folding, protein also subjected to quality control. Nascent glycoprotein (with one remaining glucose residue) binds calnexin. If properly folded, it either: functions in er as er resident protein, transported to golgi and then onward into endomembrane system. If it is misfolded, exposed hydrophobic residues that are usually masked are recognized by gt monitoring enzyme: er lumenal glucosyltransferase (ugtt) Gt monitoring enzyme adds back on a glucose. Misfolded protein rebinds to calnexin to try again. Entire process continues until it is properly folded, or . Misfolded proteins are eventually destroyed by the erad pathway. Misfolded protein translocated back out of er via the translocon (mechanism not well understood) There is an enzyme that slowly removes manose residues from core n-linked oligosaccharide; once the manose content is too low, the protein is no longer recycled; it is sent to the proteasome for degradation.