Funny you should ask. We have been discussing the unusual mobility on
SDS-PAGE of a mammalian membrane protein with heating at 65oC vs boiling.
This protein is not covalently bound to any lipid moiety. It has 10-12
membrane spans and a large soluble domain. With boiling, the antigenic band
runs at approximately 200 kDaltons. At 65oC or less, it runs at the
molecular weight predicted by amino acid sequence. Another protein that
behaves like this is one of the glucose transporters (Glut5?), also with
10-12 membrane spans and a large soluble domain and no lipid moieties.
Our explanation is purely guess...that the boiling causes aggregation; the
lower temperature allows unfolding without aggregation. Similar experiences
of others will be watched with interest.
Crescence Bookstein, Ph.D.
Research Associate/Assistant Professor
Dept of Medicine, mc6084
University of Chicago
5841 S. Maryland Ave.
Chicago, IL 60637