Human α1-proteinase inhibitor

Loebermann, Hartmut; Tokuoka, R.; Deisenhofer, Johann; Huber, Robert

doi:10.1016/0022-2836(84)90298-5

Cited by 742 publications

(298 citation statements)

References 46 publications

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“…It is well-known that covalent complex conformation between serpins and their target proteinases is associated with a cleavage of the bait peptide bond P] Pt' [32][33][34]. Therefore, in view of the observation that both neoantigenic epitopes are exposed in complexed as well as in cleaved PAl-l, it is most likely that cleavage of the P1-PI' bond is a major event responsible for the generation of these epitopes.…”

Section: Detection O]common Neoantigenic Epitopes In Various Pal1mentioning

confidence: 99%

Characterization of common neoantigenic epitopes generated in plasminogen activator inhibitor‐1 after cleavage of the reactive center loop or after complex formation with various serine proteinases

Debrock

Declerck

1995

FEBS Letters

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Plasminogen activator inhibitor-I (PAl-l), an important risk factor for thrombotic diseases, is a member of the superfamily of serine proteinase inhibitors. To define structural rearrangements occurring during interaction between PAI-I and its target proteinases we have raised monoclonal antibodies against the PAI-IIt-PA complex. Thirteen out of 401 monoclonal antibodies reacted preferentially with the PAI-IIt-PA complex as compared to free PAI-I or free t-PA. Detailed characterization revealed the presence of two non-overlapping neoantigenic epitopes in the PAI-IIt-PA complex. Both neoantigenic epitopes were also exposed after complex formation between PAI-I and either urokinase-type plasminogen activator, plasmin or thrombin as well as after cleavage of the reactive site loop of non-inhibitory substrate type PAI-I variants. Thus, we have identified two neoantigenic epitopes, localized entirely in PAl-l, and commonly exposed after complex formation of active PAI-I with various proteinases or after cleavage of substrate PAI-I. These monoclonal antibodies should facilitate further studies on the mechanism of interaction between various PAI-I forms and its target proteinases.

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Section: Detection O]common Neoantigenic Epitopes In Various Pal1mentioning

confidence: 99%

Characterization of common neoantigenic epitopes generated in plasminogen activator inhibitor‐1 after cleavage of the reactive center loop or after complex formation with various serine proteinases

Debrock

Declerck

1995

FEBS Letters

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“…As first described by Stein and Chothia (14), the conformational change associated with reactive loop insertion and inhibition is due to movement of a well defined fragment of serpin structure, consisting of helix F and strands 1, 2, and 3 of sheet A on joints formed by helices D and E. This s123AhDEF fragment moves, as a unit, away from the remainder of the serpin to open a gap between strands 3A and 5A of the native structure. It is into this gap that the reactive loop/s4A polypeptide is inserted (to varying degrees) in P14-inserted antithrombin (12,13) and inhibitory (3-6), latent (11)(12)(13), and cleaved (9,10) serpins.…”

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confidence: 99%

Identification of the Antithrombin III Heparin Binding Site

Ersdal-Badju

Zuo

et al. 1997

Journal of Biological Chemistry

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The heparin binding site of the anticoagulant protein antithrombin III (ATIII) has been defined at high resolution by alanine scanning mutagenesis of 17 basic residues previously thought to interact with the cofactor based on chemical modification experiments, analysis of naturally occurring dysfunctional antithrombins, and proximity to helix D. The baculovirus expression system employed for this study produces antithrombin which is highly similar to plasma ATIII in its inhibition of thrombin and factor Xa and which resembles the naturally occurring ␤-ATIII isoform in its interactions with high affinity heparin and pentasaccharide (Ersdal-Badju, E., Lu, A., Peng, X., Picard, V., Zendehrouh, P., Turk, B., Bjö rk, I., Olson, S. T., and Bock, S. C. (1995) Biochem. J. 310, 323-330). Relative heparin affinities of basic-to-Ala substitution mutants were determined by NaCl gradient elution from heparin columns. The data show that only a subset of the previously implicated basic residues are critical for binding to heparin. The key heparin binding residues, Lys-11, Arg-13, Arg-24, Arg-47, Lys-125, Arg-129, and Arg-145, line a 50-Å long channel on the surface of ATIII. Comparisons of binding residue positions in the structure of P14-inserted ATIII and models of native antithrombin, derived from the structures of native ovalbumin and native antichymotrypsin, suggest that heparin may activate antithrombin by breaking salt bridges that stabilize its native conformation. Specifically, heparin release of intramolecular helix D-sheet B salt bridges may facilitate s123AhDEF movement and generation of an activated species that is conformationally primed for reactive loop uptake by central ␤-sheet A and for inhibitory complex formation. In addition to providing a structural explanation for the conformational change observed upon heparin binding to antithrombin III, differences in the affinities of native, heparin-bound, complexed, and cleaved ATIII molecules for heparin can be explained based on the identified binding site and suggest why heparin functions catalytically and is released from antithrombin upon inhibitory complex formation.

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“…Based on the crystal structures of ATIII (14) and other serpins in cleaved (15,16) and uncleaved (17) forms, inhibition has been proposed to proceed through the recognition of the Arg 393 -Ser 394 bond in an exposed loop of ATIII as a substrate. However, upon cleavage, a conformational change in the inhibitor has been proposed to result in the trapping of the enzyme either as a tetrahedral intermediate or as an acyl-enzyme.…”

mentioning

confidence: 99%

Functional Requirements for Inhibition of Thrombin by Antithrombin III in the Presence and Absence of Heparin

Tsiang

Jain

Gibbs

1997

Journal of Biological Chemistry

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Mutation of 79 highly exposed amino acids that comprise approximately 62% of the solvent accessible surface of thrombin identified residues that modulate the inhibition of thrombin by antithrombin III, the principal physiological inhibitor of thrombin. Mutations that decreased the susceptibility of thrombin to inhibition by antithrombin III in the presence and absence of heparin (W50A, E229A, and R233A) also decreased hydrolysis of a small tripeptidyl substrate. These residues were clustered around the active site cleft of thrombin and were predicted to interact directly with the "substrate loop" of antithrombin III. Despite the large size of antithrombin III (58 kDa), no residues outside of the active cleft were identified that interact directly with antithrombin III. Mutations that decreased the susceptibility of thrombin to inhibition by antithrombin III in the presence but not in the absence of heparin (R89A/R93A/ E94A, R98A, R245A, K248A, K252A/D255A/Q256A) in general did not also affect hydrolysis of the tripeptidyl substrate. These residues were clustered among a patch of basic residues on a surface of thrombin perpendicular to the face containing the active site cleft and were predicted to interact directly with heparin. Three mutations (E25A, R178A/R180A/D183A, and E202A) caused a slight enhancement of inhibition by antithrombin III.Vascular injury or inflammation results in the activation of thrombin (1, 2). Thrombin cleaves and activates multiple substrates to mediate hemostasis through fibrin clot formation and platelet aggregation (3-7) and also regulates blood coagulation by activating the anticoagulant protein C pathway (8). The predominant mechanism for the clearance of thrombin is through inhibition by antithrombin III (ATIII), 1 a member of the family of serine protease inhibitors known as serpins (1, 9 -11). The physiological importance of this process is illustrated by the observation that individuals possessing inherited ATIII deficiency or insufficiency are subject to recurrent thrombosis (12).ATIII is a 58-kDa glycoprotein that inhibits thrombin in two kinetically distinct steps: the formation of a weak initial complex followed by rapid conversion to a stable complex (13). Based on the crystal structures of ATIII (14) and other serpins in cleaved (15, 16) and uncleaved (17) forms, inhibition has been proposed to proceed through the recognition of the Arg 393 -Ser 394 bond in an exposed loop of ATIII as a substrate. However, upon cleavage, a conformational change in the inhibitor has been proposed to result in the trapping of the enzyme either as a tetrahedral intermediate or as an acyl-enzyme. Unlike the intermediate typically formed with substrates, the intermediate formed between thrombin and ATIII is stable and resistant to hydrolysis perhaps due to the conformational change which may exclude water from the active site (9).The rate-limiting step in the inhibition of thrombin by ATIII is the formation of the initial complex (ϳ2 ϫ 10 5 M Ϫ1 min Ϫ1 ) which can be accelerated by 3 orders of...

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Human α1-proteinase inhibitor

Cited by 742 publications

References 46 publications

Characterization of common neoantigenic epitopes generated in plasminogen activator inhibitor‐1 after cleavage of the reactive center loop or after complex formation with various serine proteinases

Characterization of common neoantigenic epitopes generated in plasminogen activator inhibitor‐1 after cleavage of the reactive center loop or after complex formation with various serine proteinases

Identification of the Antithrombin III Heparin Binding Site

Functional Requirements for Inhibition of Thrombin by Antithrombin III in the Presence and Absence of Heparin

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