Sec23pSec24p

Sec23pSec24p refers to a heterodimeric protein complex that plays a crucial role in the endoplasmic reticulum (ER)-to-Golgi transport pathway in eukaryotic cells. This complex is a key component of the coat protein complex II (COPII) machinery, which is responsible for budding vesicles from the ER. The Sec23p subunit has GTPase-activating protein (GAP) activity towards the small GTPase Sec4p, which is essential for COPII vesicle formation. Sec24p, on the other hand, acts as a cargo receptor, recognizing and binding to specific proteins destined for transport out of the ER.

The Sec23pSec24p complex is recruited to the ER membrane by the Sec13p31p subcomplex of COPII, which is itself assembled by the integral ER membrane proteins Sec12p and Sec16p. Upon binding to the ER membrane, the Sec23pSec24p complex, in conjunction with Sec13p31p, drives the formation of the COPII coat, deforming the ER membrane to create nascent vesicles. Sec24p's ability to bind to a diverse array of cargo molecules, including transmembrane proteins, soluble proteins, and lipids, ensures that the correct molecular contents are packaged into the budding vesicles. Defects in Sec23pSec24p function can lead to impaired protein trafficking, ER stress, and a variety of cellular dysfunctions, highlighting its indispensable role in maintaining cellular homeostasis and protein secretion.