Electron spin resonance study of the role of nitrosyl-heme in the activation of guanylate cyclase by nitrosoguanidine and related agonists.

One major component of lens plasma membrane is a glycoprotein that SDS-polyacrylamide gel electrophoresis shows to possess an apparent molecular weight of 26,000. When this protein is solubilized in low ionic strength buffers containing SDS, and heated to 100° for 1 to 3 min prior to electrophoresis, conversion into high molecular weight aggregate results. The heat lability of this protein is greatly enhanced if it solubilized and heated in buffers containing 0.1 M NaCl. At this ionic strength, incubation for 3 h at 38° results in conversion of 20% of the protein into high melecular weight aggregates. Most other membrane proteins isolated from lens membrane are insensitive to heat treatment. It is concluded that temperature and ionic strength must be recorded and controlled carefully when using SDS-polyacrylamide gel electrophoresis to study this membrane protein.