Sec24p

Sec24p is a crucial protein component of the Saccharomyces cerevisiae SEC24 gene product. It functions as a subunit of the coat protein complex II (COPII) machinery, which is responsible for the formation of transport vesicles that bud from the endoplasmic reticulum (ER). Sec24p is specifically involved in the cargo recognition and selection process, ensuring that correctly folded proteins and other essential molecules are packaged into COPII vesicles for transport to the Golgi apparatus and beyond.

The Sec24p protein contains a pleckstrin homology (PH) domain and a beta-sheet-rich domain. These structural features enable it to interact with both the cargo molecules and the other components of the COPII coat, such as Sec13p and Sec31p. Sec24p plays a critical role in distinguishing between proteins that are destined for secretion or insertion into cellular membranes and those that need to remain within the ER. Mutations in the SEC24 gene can lead to defects in protein trafficking, resulting in mislocalization of proteins and cellular dysfunction.

There are multiple paralogs of Sec24p in higher eukaryotes, suggesting an evolutionarily conserved role in ER-to-Golgi transport. Different Sec24p paralogs can have distinct or overlapping cargo specificities, allowing for finer control over the protein sorting process. This complexity highlights the importance of Sec24p in maintaining the secretory pathway's integrity and functionality.