Growth cone particle (GCP) membranes prepared from fetal day 17 rat brain are comprised of 5 major polypeptides as analyzed by SDS-PAGE: tubulin (p52), actin (p42), pp46/GAP-43 and two unidentified ...species, p38 and p34. Antibodies specific for the alpha- and beta-subunits of G proteins recognize p38 and p34, respectively, on immunoblots following one- and two-dimensional electrophoretic separation. That G protein subunits comprise major species of GCP membrane-associated polypeptides suggests a role for G proteins in transmembrane signaling in nerve growth cones.
The sarcoglycan complex is known to be involved in limb-girdle muscular dystrophy (LGMD) and is composed of at least three
proteins: α-, β-, and γ-sarcoglycan. δ-Sarcoglycan has now been ...identified as a second 35-kDa sarcolemmal transmembrane glycoprotein
that shares high homology with γ-sarcoglycan and is expressed mainly in skeletal and cardiac muscle. Biochemical analysis
has demonstrated that γ- and δ-sarcoglycan are separate entities within the sarcoglycan complex and that all four sarcoglycans
exist in the complex on a stoichiometrically equal basis. Immunohistochemical analysis of skeletal muscle biopsies from patients
with LGMD2C, LGMD2D, and LGMD2E demonstrated a reduction of the entire sarcoglycan complex in these muscular dystrophies.
Furthermore, we have mapped the human δ-sarcoglycan gene to chromosome 5q33-q34 in a region overlapping the recently linked
autosomal recessive LGMD2F locus.
Limited primary sequence data have been obtained for all three subunits of the fourth component of murine complement (C4) and its related homologue, the sex-limited protein (Slp). These data show a ...high degree of NH2-terminal homology between C4 and Slp: four of the six residues identified for the α chain, seven of eight for the β chain, and four of four for the γ chain. This suggests that apparent molecular weight differences between C4 and Slp subunits are not, as previously suggested, due to a shift in the proteolytic processing sites in the pro-Slp polypeptide molecule. Chemical deglycosylation (apparently complete) of the C4 and Slp α chains with trifluoromethanesulfonic acid removes the molecular weight difference between them, suggesting that acquisition of extra glycosylation sites in the latter is responsible for this difference.
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