Introduction

Figure 1. This image shows the location of the DGAT protein within the Endoplasmic Reticulum Membrane

DGAT, or Diacylglycerol Acyltransferase is a polytopic endoplasmic reticulum membrane protein embedded within the membrane of the ER. DGAT is highly expressed in epithelial cells of the small intenstine of homo sapiens. It can also be found in the liver, where it helps synthesize fats for storage, and the female mammary glands, where it produces fat in the milk.

DGAT was originally discovered by its homology to Acyl-CoA cholesterol acyltransferases (ACAT) 1 and 2. The structure, catalytic mechanism of diacylglycerol acyltransferase, and how DGAT interacts with CoA was discovered using a Cryo-EM. The Cryo-EM map revealed that DGAT forms a dimer, with each subunit containing nine transmembrane helices. The N and C terminals of each helice are located on the cytosolic and luminal sides of the endoplasmic reticulum membrane respectively.

Function

DGAT makes triglycerides from a diglyceride in plasma. In order to do this, DGAT uses two substrates: a fatty acyl-CoA and a diacylglycerol substrate. The basic mechanism consists of a lone pair on a hydroxyl group of glycerol attacking the carbon of the thioester bond of CoA. This results in the breakage of the thioester bond, and the attached acyl group attaches to the glycerol, creating a triglyceride.

Structure

Tunnels

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