Effects of prothrombin fragments on thrombin, on thrombin formation, and separation from Ac-globulin (factor V)

Seegers, Walter H.; Novoa, Eduardo; Walz, Daniel A.; Andary, Thomas J.; Hassouna, Houria I.

doi:10.1016/0049-3848(76)90126-2

Cited by 16 publications

(2 citation statements)

References 25 publications

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“…Thus, isolated kringle 1 and kringle 4 fragments of plasminogen retain their capacity to bind o-aminocarboxylic acids (1,17), isolated kringle 5 binds to benzamidine-Sepharose (18), and fragment 2 of prothrombin, corresponding to one of the prothrombin kringles, carries an intact binding site for factor Va (8,19).…”

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confidence: 99%

Folding autonomy of the kringle 4 fragment of human plasminogen.

Trexler

Patthy

1983

Proc. Natl. Acad. Sci. U.S.A.

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Kringle 4, an 88-residue plasminogen fragment carrying a lysine-binding site, loses its affinity for lysine-Sepharose upon reductive cleavage of its disulfide bridges. Aerobic incubation of the reduced, denatured fragment results in the rapid restoration of the disulfide bonds with concomitant recovery of lysine-Sepharose affinity. The ability of the unfolded fragment to regain its native conformation suggests that the kringle structure is an autonomous folding domain. During refolding of kringle 4 the native disulfide bonds, Cys22 Cys62 and Cys50 Cys74, appear first. The folding intermediate possessing these two disulfide bridges already binds to lysine-Sepharose, indicating that the third native bridge, which in native kringle 4 connects residues Cys' and Cys79, is not essential for the maintenance of the biologically active conformation of kringle 4. Comparison of the sequences of human prothrombin, urokinase, and plasminogen kringles revealed that the residues surrounding the (Cys22 Cys62 and Cys5" Cys74 bridges constitute the most conservative segments of kringles, whereas the residues neighboring the Cys' Cys79 bridge are not highly conserved. We propose that conservation of various residues in the different kringles reflects their importance for the folding autonomy of kringles.Plasminogen, prothrombin, and urokinase, unlike the proenzymes of pancreatic serine proteases, possess large protein extensions at the amino-terminal end of the homologous protease part (1-4). These nonprotease segments are important for the biological specificity and control ofplasmin, thrombin, and urokinase because they are involved in interactions that regulate plasminogen activation and plasmin-catalyzed fibrinolysis (5) or control the prothrombin-thrombin conversion (6). Thus, the nonprotease regions participate in the Ca2+-mediated binding of prothrombin to phospholipid membranes, in the association of prothrombin with factor Va (7,8), and in the interactions of plasmin(ogen) with fibrin, a2-antiplasmin, and w-aminocarboxylic acids (9-11).The multiplicity of binding functions associated with the nonprotease segments of prothrombin, plasminogen, and urokinase is reflected in the structure of these proteins inasmuch as these regions are divided into discrete structural-functional units. In the case of plasminogen five triple-loop, three-disulfide-bridge "kringles" are discernible in the nonprotease segment (1). The five structural units display identical gross architecture and remarkable sequence homology, making the conclusion inescapable that these units arose as a result of 5-fold internal repetition of the same gene piece (12, 13). The aminoterminal part of prothrombin also contains two kringles, closely homologous to those of plasminogen (2, 3); the kringles of plasminogen and prothrombin are in fact more closely related than their protease parts (12). Urokinase was also shown recently to possess a kringle structure that shows extensive homology with the prothrombin and plasminogen kringles (4).

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mentioning

confidence: 99%

Folding autonomy of the kringle 4 fragment of human plasminogen.

Trexler

Patthy

1983

Proc. Natl. Acad. Sci. U.S.A.

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“…In contrast to alpha-thrombin, only very little knowledge exists about the biological function of the intermediates of prothrombin activation. It is known that meizothrombin has reduced activity towards macromolecular substrates (3,14,15), but is effective in the activation of protein C (16). Meizothrombin might be a potent agonist for vascular contraction.…”

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confidence: 99%

Intermediates of Prothrombin Activation Induce Intracellular Calcium Mobilization in Rat Aortic Smooth Muscle Cells

Kaufmann

Hoffmann²,

Ramakrishnan³

et al. 1998

Thromb Haemost

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SummaryWhile effects of alpha-thrombin have been well characterized in different cell types, the biological function of intermediates of prothrombin activation is still undefined. Meizothrombin could be shown to be a potent agonist for vascular contraction which seems to be mediated by an interaction with the vascular smooth muscle. To explore this effect at intracellular signaling level, we used rat aortic smooth muscle cells and investigated the effect of the intermediates formed by cleavage of human prothrombin with ecarin, the prothrombin activator from Echis carinatus venom, on mobilization of free intracellular calcium. The ecarin-activated prothrombin induced very rapidly transient calcium mobilization in SMC´s comparable to that observed with alpha-thrombin. We conclude that meizothrombin/ meizothrombin desF1 (MT/MT desF1) are the most likely candidates for this effect. Furthermore, our results suggest the involvement of PAR-1-type thrombin receptors in MT/MT desF1-induced calcium signaling in rat aortic smooth muscle cells.

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