期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1998
卷号：95
期号：18
页码：10511-10516
DOI：10.1073/pnas.95.18.10511
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Elongated fibrinogen molecules are comprised of two outer "D" domains, each connected through a "coiled-coil" region to the central "E" domain. Fibrin forms following thrombin cleavage in the E domain and then undergoes intermolecular end-to-middle D:E domain associations that result in double-stranded fibrils. Factor XIIIa mediates crosslinking of the C-terminal regions of {gamma} chains in each D domain (the {gamma}XL site) by incorporating intermolecular {varepsilon}-({gamma}-glutamyl)lysine bonds between amine donor {gamma}406 lysine of one {gamma} chain and a glutamine acceptor at {gamma}398 or {gamma}399 of another. Several lines of evidence show that crosslinked {gamma} chains extend "transversely" between the strands of each fibril, but other data suggest instead that crosslinked {gamma} chains can only traverse end-to-end-aligned D domains within each strand. To examine this issue and determine the location of the {gamma}XL site in fibrinogen and assembled fibrin fibrils, we incorporated an amine donor, thioacetyl cadaverine, into glutamine acceptor sites in fibrinogen in the presence of XIIIa, and then labeled the thiol with a relatively small (0.8 nm diameter) electron dense gold cluster compound, undecagold monoaminopropyl maleimide (Au11). Fibrinogen was examined by scanning transmission electron microscopy to locate Au11-cadaverine-labeled {gamma}398/399 D domain sites. Seventy-nine percent of D domain Au11 clusters were situated in middle to proximal positions relative to the end of the molecule, with the remaining Au11 clusters in a distal position. In fibrin fibrils, D domain Au11 clusters were located in middle to proximal positions. These findings show that most C-terminal {gamma} chains in fibrinogen or fibrin are oriented toward the central domain and indicate that {gamma}XL sites in fibrils are situated predominantly between strands, suitably aligned for transverse crosslinking.
