In:
European Journal of Biochemistry, Wiley, Vol. 167, No. 3 ( 1987-09), p. 405-411
Abstract:
The horseshoe crab clotting factor, factor C, present in the hemocytes is a serine‐protease zymogen activated with lipopolysaccharide. It is a two‐chain glycoprotein ( M r = 123 000) composed of a heavy chain ( M r = 80 000) and a light chain ( M r = 43 000) [T. Nakamura et al. (1986) Eur. J. Biochem. 154 , 511–521]. In our continued study of this zymogen, we have now also found a single‐chain form of factor C ( M r = 123 000) in the hemocyte lysate. The heavy chain had the NH 2 ‐terminal sequence of Ser‐Gly‐Val‐Asp‐, consistent with that of the single‐chain factor C, indicating that the heavy chain is derived from the NH 2 ‐terminal part of the molecule. The light chain had an NH 2 ‐terminal sequence of Ser‐Ser‐Gln‐Pro‐. Incubation of the two‐chain zymogen with lipopolysaccharide resulted in the cleavage of a Phe‐Ile bond between residues 72 and 73 of the ligth chain. Concomitant with this cleavage, the A (72 amino acid residues) and B chains derived from the light chain were formed. The complete amino acid sequence of the A chain was determined by automated Edman degradation. The A chain contained a typical segment which is similar in sequence to a family of repeats in human β 2 ‐glycoprotein I, complement factors B, protein H, C4b‐binding protein, and coagulation factor XIII b subunit. The NH 2 ‐terminal sequence of the B chain was Ile‐Trp‐Asn‐Gly‐. This chain contained the serine‐active site sequence‐ Asp‐ Ala‐Cys‐Ser‐Gly‐Asp‐ Ser‐ Gly‐Gly‐Pro‐. These results indicate that horseshoe crab factor C exists in the hemocytes in a single‐chain zymogen form and is converted to an active serine protease by hydrolysis of a specific Phe‐Ile peptide bond.
Type of Medium:
Online Resource
ISSN:
0014-2956
,
1432-1033
DOI:
10.1111/ejb.1987.167.issue-3
DOI:
10.1111/j.1432-1033.1987.tb13352.x
Language:
English
Publisher:
Wiley
Publication Date:
1987
detail.hit.zdb_id:
1398347-7
detail.hit.zdb_id:
2172518-4
SSG:
12