endoplasmic reticulum (ER)

Introduction

The ER consists of a continuous sheet of highly folded membranes, extending from the outer nuclear membrane. It is the site of translation, folding, post-translational modification (glycosylation, disulfide bond formation), & transport of proteins destined to integrate into the plasma membrane or enter the secretory pathway of secreted proteins. The GOLGI receives nascent polypeptides from the ER destined for the secretory pathway.

Main site of fatty acid & cholesterol biosynthesis.

The signal recognition sequence (SRS) targets translation products to the rough endoplasmic reticulum (ER).

The KDEL motif retains proteins within the lumen of the ER via the KDEL receptor.

Function

• the ER is the site of translation, folding, post-translational modificati (glycosylation, disulfide bond formation), & transport of proteins destined to integrate into the plasma membrane or enter the secretory pathway of secreted proteins
• the GOLGI receives nascent polypeptides from the ER destined for the secretory pathway
• ransfer of membranes from the endoplasmic reticulum to the Golgi occurs via 50-70 nm transition vesicles which derive from part-rough, part-smooth transitional elements of the endoplasmic reticulum (t-ER)
• vesicle budding from the t-ER is an ATP-dependent process
• ER is the main site of fatty acid & cholesterol biosynthesis
• the signal recognition sequence (SRS) targets translation products to the rough endoplasmic reticulum (ER)
• the KDEL motif retains proteins within the lumen of the ER via the KDEL receptor

Structure

• the ER consists of a continuous sheet of highly folded membranes, extending from the outer nuclear membrane

More general terms

• organelle
• intracellular membrane

More specific terms

• smooth endoplasmic reticulum

Additional terms

• KDEL motif (endoplasmic retention consensus sequence)
• signal recognition sequence (SRS)