Human MLEC (Malectin) knockout HeLa cell lysate

Supplementary information

This supplementary information is collated from multiple sources and compiled automatically.

Malectin also known as MLEC is a membrane-bound protein involved in glycoprotein quality control. It has a mass of approximately 25 kDa and is expressed in the endoplasmic reticulum (ER). Malectin functions by binding to specific N-linked glycan structures on nascent glycoproteins ensuring proper folding and quality control processes. It operates within the cellular machinery that governs glycoprotein maturation and export.

Biological function summary

Malectin plays an essential role in the ER's function as a molecular chaperone. It forms part of a quality control complex that monitors and assists in the folding of glycoproteins preventing misfolded or improperly assembled proteins from exiting the ER. This process is critical for maintaining cellular homeostasis and proper protein function. The interaction of Malectin with other ER-resident proteins ensures that only correctly folded proteins progress through the secretory pathway.

Pathways

Malectin's activity is integral to the calnexin/calreticulin cycle contributing to the glycoprotein folding pathway. This pathway is important for the maturation of glycoproteins and involves interactions with other proteins such as calnexin and calreticulin which facilitate proper folding and stabilization. Malectin aids in the retention of misfolded proteins within the ER collaborating with the glycosyl transfer enzyme UDP-glucose:glycoprotein glucosyltransferase 1 to ensure quality control before proteins are transported further along the secretory pathway.

Malectin appears relevant to conditions like congenital disorders of glycosylation (CDG) and cystic fibrosis. Disruptions in Malectin function can affect the glycoprotein folding pathway leading to faulty glycosylation patterns associated with CDG. Additionally Malectin intersects with the cystic fibrosis transmembrane conductance regulator (CFTR) in cystic fibrosis where improper folding and trafficking of CFTR result in disease symptoms. Understanding Malectin's role could illuminate new strategies for addressing malfunctions in glycoprotein handling related to these disorders.