The effects of proteases on proteins and glycoproteins of Dictyostelium discoideum plasma membranes

doi:10.1016/0014-4827(77)90292-0

Experimental Cell Research

Volume 110, Issue 2, December 1977, Pages 267-276

https://doi.org/10.1016/0014-4827(77)90292-0 Get rights and content

Abstract

Dictyostelium discoideum cells were incubated with proteases, the plasma membranes subsequently isolated and changes in proteins and glycoproteins examined with dodecylsulfate gel electrophoresis. Low papain concentrations gave rise to a protein band which apparently derived from actin. Since actin was the only protein attacked, the results suggest some part of the actin is exposed on the outer surface of the cell. Higher papain concentrations released a substantial portion of actin from the plasma membrane and partially digested some of the glycoproteins. Since the new actin-derived band was not further digested, the glycoproteins may be required to stabilize the actin polymer rather than anchor those actin molecules which are directly associated with the plasma membrane. Pronase treatment released the two myosin heavy chains from the plasma membrane, in particular the higher molecular weight chain. Actin was not affected. Some glycoproteins were digested. Trypsin attacked many of the plasma membrane proteins, and the myosin heavy chains were completely removed. Actin was only moderately affected. However, the glycoproteins were entirely resistant to trypsin. Apparently the myosin heavy chains are attacked either due to their partial exposure on the cell surface or the exposure of proteins which anchor them in the membrane. These anchoring proteins cannot be glycoproteins or actin. Proteins and glycoproteins were largely digested when isolated plasma membranes were incubated with papain and pronase. The effects of trypsin on whole cells and isolated plasma membranes were similar.

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^☆: This work was supported by the Schweizerischer Nationalfonds zur Förderung der wissenschaftlichen Forschung (Grant 3.673-0.75).

¹: Present address: Biochemical Institute, ETH, Zürich.

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The effects of proteases on proteins and glycoproteins of Dictyostelium discoideum plasma membranes☆

Abstract

Exp cell res

J mol biol

J biol chem

FEBS lett

J biol chem

J mol biol

Cell

Biochim biophys acta

FEBS lett

FEBS lett

FEBS lett