Transfected cDNA directs expression of hemolytically active murine C4 in cultured mouse and monkey cells.
Previously cloned and sequenced full-length cDNAs for murine C4 and the closely related sex-limited protein (Slp) have been placed into an eucaryotic expression vector. Transfer of these DNA constructs transiently into monkey COS cells or stably into mouse L cells results in the expression and secretion of hemolytically active mouse C4 and mature Slp. We estimate from hemolytic activities that COS and L cells secrete 0.04 and 3%, respectively, of the C4 level found in mouse plasma. Slp expression is consistently only 10-20% that of C4 although the identical expression system is used for both. Our results show subtle but reproducible cell-type-specific differences in C4 maturation; they also indicate that surprisingly large shifts in electrophoretic mobility on SDS-polyacrylamide gels are induced by a small number of amino acid substitutions. The expression of C4 from cDNAs of known sequence provides a starting point for studies of structure/function relationships in C4 employing site-specific mutagenesis and gene transfer.
Picchi
M A
MA
Department of Molecular Biology, Research Institute of Scripps Clinic, La Jolla, Calif.
Bradt
B M
BM
Cooper
N R
NR
Ogata
R T
RT
D000818:Animals; D001798:Blood Proteins / Q000378:metabolism; D002478:Cells, Cultured; D003181:Complement C4 / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D015941:Complement Hemolytic Activity Assay; D000882:Haplorhini; D006461:Hemolysis / Q000235:genetics*; D066298:In Vitro Techniques; D051379:Mice; D010957:Plasmids; D011233:Precipitin Tests; D014162:Transfection / Q000235:genetics*
D001798:Blood Proteins; C018386:C4a protein, mouse; D003181:Complement C4