Limited proteolysis of complement components C2 and factor B. Structural analogy and limited sequence homology.
A method is described for the simultaneous purification of milligram quantities of complement components C2 and Factor B. Both products are homogeneous by the criteria of polyacrylamide-gel electrophoresis and N-terminal sequence analysis. Component C2 is cleaved by serine proteinase C1s at an X-Lys bond to give fragment C2a (approx. mol.wt. 74000) and fragment C2b (approx. mol.wt. 34000). The two fragments can be separated by gel filtration without the need for reducing or denaturing agents. Fragment C2b represents the N-terminal end of the molecule. Similar results were seen on cleavage of Factor B by Factor D in the presence of component C3. Again two non-covalently linked fragments are formed. The smaller, fragment Ba (approx. mol.wt. 36,000),) has threonine as the N-terminal residue, as does Factor B; the larger, fragment Bb (approx. mol. wt. 58000), has lysine as the N-terminal residue. A similar cleavage pattern is obtained on limited proteolysis of Factor B by trypsin, suggesting an Arg-Lys-or Lys-Lys bond at the point of cleavage. Although component C2 and Factor B show no apparent N-terminal sequence homology, a limited degree of sequence homology is seen around the sites of proteolytic cleavage.
D000595:Amino Acid Sequence; D002850:Chromatography, Gel; D003172:Complement C1; D003175:Complement C2 / Q000302:isolation & purification; D011415:Complement Factor B / Q000302:isolation & purification; D011416:Complement Factor D; D004591:Electrophoresis, Polyacrylamide Gel; D004792:Enzyme Precursors / Q000302:isolation & purification; D006801:Humans; D008722:Methods; D010446:Peptide Fragments / Q000032:analysis; D014357:Trypsin
D003172:Complement C1; D003175:Complement C2; D004792:Enzyme Precursors; D010446:Peptide Fragments; D014357:Trypsin; C493488:CFD protein, human; D011416:Complement Factor D; D011415:Complement Factor B
Scand J Immunol. 1976;5(9):1049-55
1006167
Biochemistry. 1977 Nov 29;16(24):5368-75
411505
Biochem J. 1978 Apr 1;171(1):99-107
417728
Proc Natl Acad Sci U S A. 1977 Jul;74(7):2998-3001
70787
Trans Assoc Am Physicians. 1977;90:174-83
148134
Biochem J. 1978 Nov 1;175(2):675-84
743217
Biochem J. 1977 Sep 1;165(3):439-46
921758
Biochemistry. 1976 Oct 5;15(20):4513-21
823964
Biochem J. 1976 Sep 1;157(3):541-8
985398
Nature. 1976 Oct 14;263(5578):613-4
980109
J Immunol. 1974 Dec;113(6):1735-43
4279261
J Exp Med. 1973 Dec 1;138(6):1305-13
4202731
Biochem J. 1976 Apr 1;155(1):5-17
7240
Biochemistry. 1975 Sep 23;14(19):4245-51
241376
J Immunol. 1973 Jan;110(1):128-38
4734384
Biochemistry. 1975 Nov 18;14(23):5088-94
1238107
Biochemistry. 1975 Jul;14(13):3029-35
1148190
Nature. 1970 Aug 15;227(5259):680-5
5432063
J Exp Med. 1968 Sep 1;128(3):533-51
5666963
J Exp Med. 1967 Feb 1;125(2):359-80
6019133