UNIT 15.3 Endocytosis: Biochemical Analyses

  1. Timothy E. McGraw,
  2. Agathe Subtil

Published Online: 1 MAY 2001

DOI: 10.1002/0471143030.cb1503s03

Current Protocols in Cell Biology

Current Protocols in Cell Biology

How to Cite

McGraw, T. E. and Subtil, A. 2001. Endocytosis: Biochemical Analyses. Current Protocols in Cell Biology. 3:15.3:15.3.1–15.3.23.

Author Information

  1. Weill Medical School of Cornell University, New York, New York

Publication History

  1. Published Online: 1 MAY 2001
  2. Published Print: JUL 1999


Many integral membrane proteins synthesized in the endoplasmic reticulum ultimately arrive at the cell surface to contact the cell environment. During transit through the Golgi and trans-Golgi network, proteins acquire post-translational modifications that can be used to track the appearance of such modified proteins at the cell surface. Cellular proteins can be treated with enzymes--e.g., sialidase or protease--or antibodies, or biotinylated to identify molecules that have reached the cell surface. Some proteins first enter the endocytic pathway before appearing at the cell surface; this is detected by treating the cells at 4o and 37oC. Analysis of the number of sialic acids on proteins of cells treated at 4oC identifies proteins resident at the cell surface, while cells treated at 37oC internalize the sialidase, which can then act with proteins in the endocytic compartments.