M. Edidin et al., TRUNCATION MUTANTS DEFINE AND LOCATE CYTOPLASMIC BARRIERS TO LATERAL MOBILITY OF MEMBRANE-GLYCOPROTEINS, Proceedings of the National Academy of Sciences of the United Statesof America, 91(8), 1994, pp. 3378-3382
The lateral mobility of cell membrane glycoproteins is often restricte
d by dynamic barriers. These barriers have been detected by measuremen
ts of fluorescence photo-bleaching and recovery (FPR) and barrier-free
path (BFP). To define the location and properties of the barriers, we
compared the lateral mobility, measured by FPR and BFP, of wild-type
class I major histocompatibility complex (MHC) membrane glycoproteins
with the lateral mobility of mutant class I MHC glycoproteins truncate
d in their cytoplasmic domains. Mutants with 0 or 4 residues in the cy
toplasmic domain were as mobile as lipid-anchored class I MHC molecule
s, molecules whose lateral mobility is relatively unrestricted by barr
iers. In contrast, mobility of class I MHC molecules with 7-residue cy
toplasmic domains was as restricted as mobility of class I molecules w
ith full-length, 31-residue cytoplasmic domains. Though some of the di
fference between the mobilities of mutants with 4- or 0-residue domain
s and the other class I molecules may be due to differences in the net
charge of the cytoplasmic domain, FPR measurements of the mobility of
molecules with 7-residue domains show that length of the cytoplasmic
domain has an important influence on the lateral mobility. Model calcu
lations suggest that the barriers to lateral mobility are 2-3 nm below
the membrane bilayer.