Why Are Endosomes Acidic?

The internal environment of an endosome is acidic (pH 5-6). This is maintained by an ATP-driven H+ pump in the endosomal membrane. This acidic environment is crucial to the endosome's role of sorting as it causes many receptors to release their bound cargo, thus enabling the recycling of membrane proteins.

What is the significance of pH in endosome maturation?

Thus, the membrane sorting that occurs in endosomes is important for regulating cell physiology. The pH levels in endosomes play an important role in many functions of endocytosis, including release of iron from transferrin, release of LDL and other ligands from their receptors, and activation of lysosomal hydrolases.

What does acidification of the endosome do?

Influenza viruses enter the cell inside an endosome. During the endosomal journey, acidification triggers a conformational change of the virus spike protein hemagglutinin (HA) that results in escape of the viral genome from the endosome into the cytoplasm.