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Structural requirements for Ca2+ binding to the gamma-carboxyglutamic acid and epidermal growth factor-like regions of factor IX. Studies using intact domains isolated from controlled proteolytic digests of bovine factor IX

In English

Författare

Summary, in English

Blood coagulation factor IX is composed of discrete domains with an NH2-terminal vitamin K-dependent gamma-carboxyglutamic acid (Gla)-containing region, followed by two domains that are homologous with the epidermal growth factor (EGF) precursor and a COOH-terminal serine protease part. Calcium ions bind to the Gla-containing region and to the NH2-terminal EGF-like domain. To be able to determine the structure and function of the Gla- and EGF-like domains, we have devised a method for cleaving factor IX under controlled conditions and isolating the intact domains in high yield, either separately or linked together. The Ca2+ and Mg2+ binding properties of these fragments were examined by monitoring the metal ion-induced changes in intrinsic protein fluorescence. A fragment, consisting of the Gla region linked to the two EGF-like domains, bound Ca2+ in a manner that was indistinguishable from that of the intact molecule, indicating a native conformation. The Ca2+ affinity of the isolated Gla region was lower, suggesting that the EGF-like domains function as a scaffold for the folding of the Gla region. The Gla-independent high affinity metal ion binding site in the NH2-terminal EGF-like domain was shown to bind Ca2+ but not Mg2+. A comparison with similar studies of factor X (Persson, E., Bjork, I., and Stenflo, J. (1991) J. Biol. Chem. 266, 2444-2452) suggests that the Ca2(+)-induced fluorescence quenching is due to an altered environment primarily around the tryptophan residue in position 42.

Publiceringsår

1991

Språk

Engelska

Sidor

2430-2437

Publikation/Tidskrift/Serie

Journal of Biological Chemistry

Volym

266

Issue

4

Dokumenttyp

Artikel i tidskrift

Förlag

American Society for Biochemistry and Molecular Biology

Ämne

  • Medicinal Chemistry

Status

Published

Forskningsgrupp

  • Clinical Chemistry, Malmö

ISBN/ISSN/Övrigt

  • ISSN: 1083-351X