SAR1A Human

GTP-Binding Protein SAR1A, also known as SAR1A, is a small GTPase that plays a crucial role in vesicle-mediated transport from the endoplasmic reticulum (ER) to the Golgi apparatus. This protein is part of the coat protein complex II (COPII), which is essential for the formation of transport vesicles . SAR1A cycles between an active GTP-bound state and an inactive GDP-bound state, facilitating the recruitment of other COPII components to the ER membrane .

The recombinant form of SAR1A is typically produced using bacterial expression systems. The gene encoding SAR1A is cloned into an expression vector, which is then introduced into a suitable bacterial host, such as Escherichia coli. The bacteria are cultured, and the expression of SAR1A is induced. The protein is then purified using affinity chromatography techniques, often involving a His-tag for easy purification . The purified protein is stored in a buffer containing Tris-HCl, DTT, and glycerol to maintain its stability .

SAR1A’s function is regulated by its ability to bind and hydrolyze GTP. In its GTP-bound form, SAR1A inserts into the ER membrane, initiating the assembly of the COPII coat. This process involves the recruitment of other COPII components, such as Sec23/24 and Sec13/31 complexes, which form the vesicle coat. The hydrolysis of GTP to GDP by SAR1A triggers a conformational change, leading to the disassembly of the COPII coat and the release of the vesicle .

The activity of SAR1A can be analyzed using various biochemical assays. GTPase assays measure the hydrolysis of GTP to GDP, providing insights into the protein’s enzymatic activity. Additionally, binding assays can be used to study the interaction between SAR1A and other COPII components. Structural studies, such as X-ray crystallography and NMR spectroscopy, have provided detailed insights into the conformational changes that occur during the GTPase cycle .