Murine complement component C4 and sex-limited protein: identification of amino acid residues essential for C4 function.

The complement component C4 of mammals.

Human complement component C4 is coded by tandem genes located in the HLA class III region. The products of the two genes, C4A and C4B, are different in their activity. This difference is due to a degree of 'substrate' specificity in the covalent binding reactions of the two isotypes. Mouse also has a duplicated locus, but only one gene produces active C4, while the other codes for the closely ...

Amino acid sequence homologies and glycosylation differences between the fourth component of murine complement and sex-limited protein.

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 alpha chain, seven of eight for the beta chain, and four of four for the gamma chain. This suggest...

Immunity in C4-Deficient Mice Component C4 Can Restore Humoral Macrophage-Derived Complement

Cell-free synthesis of the fourth component of guinea pig complement (C4): identification of a precursor of serum C4 (pro-C4).

Polysomes (S-20) from homogenates of guinea pig liver synthesized serum albumin and a precursor of the fourth component of guinea pig complement (C4) in vitro. The C4 precursor (pro-C4) accounted for approximately 0.2% and albumin 4% of the radiolabeled protein precipitable by trichloroacetic acid and not bound to polysomes. Pro-C4 is a single polypeptide chain (molecular weight 200,000) which ...

Sex, MHC and complement C4 in autoimmune diseases.

Autoimmune diseases are estimated to affect 10-50 million people in the United States, and untold millions worldwide. Nearly 80% of all people with autoimmune diseases are women, and a strong association of these diseases with MHC genes has been known for some time. However, very little is known about what causes autoimmune diseases or the factors that lead to disease recurrence. The sex-associ...