Interaction of Streptokinase and Human Plasminogen

Buck, Friedrich; Boggiano, E.

doi:10.1016/s0021-9258(19)77193-2

Cited by 20 publications

(5 citation statements)

References 25 publications

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“…Through undefined mechanisms, SK is able to generate or unmask this active site without cleavage (McClintock & Bell, 1971). Previous studies are consistent with the hypothesis that streptokinase has at least three functions in the generation of a functional plasminogen activator complex: (1) high-affinity binding to plasminogen to form a complex; (2) interacting with plasminogen to generate the active site; (3) binding and processing of substrate plasminogen molecules (Buck & Boggiano, 1971;Reed et al, 1995). Unfortunately, the molecular mechanisms underlying these functions remain unknown.…”

supporting

confidence: 75%

Mutation of Lysines in a Plasminogen Binding Region of Streptokinase Identifies Residues Important for Generating a Functional Activator Complex

et al. 1996

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Through a unique but poorly understood mechanism, streptokinase (SK) interacts with human plasminogen to generate an "activator complex" that efficiently cleaves substrate plasminogen molecules. Previous studies have suggested that lysine residues in SK may play a role in the binding and function of the activator complex. To investigate this hypothesis, 10 different lysine residues in the plasminogen binding region of SK were altered to construct 8 recombinant (r) SK mutants. Only one double mutant, rSKK256,257A (replacing Lys with Ala at residues 256 and 257), showed a statistically significant reduction (63%) in binding affinity for Glu-plasminogen. This mutant also displayed a lagtime in the appearance of maximal activity, and modest impairments (2-5-fold) in kinetic parameters for amidolytic and plasminogen activator activity compared to rSK. In contrast, another mutant, rSKK332,334A, formed an activator complex with profound and nearly selective defects in the catalytic processing of substrate plasminogen molecules. When compared to rSK in kinetic assays of plasminogen activation, the rSKK332,334A mutant formed an activator complex that bound substrate plasminogens normally (normal K(m), but its ability to activate or cleave these molecules (kcat) was reduced by 34-fold. In contrast, in amidolytic assays, the kinetic parameters of rSKK332,334A showed only minor differences (< 2-fold) from rSK. Similarly, the binding affinity of this mutant to human Glu-plasminogen was indistinguishable from rSK [(2.6 +/- 0.8) x 10(9) vs (2.4 +/- 0.2) x 10(9) M-1, respectively]. In summary, these experiments have identified lysine residues in a plasminogen binding region of SK which appear to be necessary for normal high-affinity binding to plasminogen, and for the efficient catalytic processing of substrate plasminogen molecules by the activator complex.

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confidence: 75%

Mutation of Lysines in a Plasminogen Binding Region of Streptokinase Identifies Residues Important for Generating a Functional Activator Complex

et al. 1996

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“…tein substrates (azocasein) are not accessible to this active site (Reddy and Markus, 1972). Bovine plasminogen, however, is directed to the active site in the activator complex, most likely due to specific interactions between bound streptokinase and bovine plasminogen (Buck and Boggiano, 1971).…”

Section: Discussionmentioning

confidence: 99%

“…Although the general proteolytic activity of plasmin is lost as a direct consequence of complexing with streptokinase, there is a parallel increase in activity of this complex toward bovine plasminogen activation. It has been proposed that this is due to streptokinase directing bovine plasminogen into the active site of the complex (Buck and Boggiano, 1971). Again, maximal activity is found at a 1:1 stoichiometry of streptokinase and human plasmin.…”

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confidence: 99%

Interaction of streptokinase and rabbit plasminogen

Schick¹

1973

Biochemistry

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The ability of rabbit plasminogen and plasmin to form complexes with streptokinase has been studied and compared to the human system. At 1 : l or 1O:l ratios of streptokinase to rabbit plasminogen, no complex was observed by sucrose density centrifugation; however, almost all the rabbit plasminogen was converted to plasmin. Under identical conditions with human plasminogen, a complex was formed which consisted of altered streptokinase and human plasmin. When the acylating agent p-nitrophenyl p'-guanidinobenzoate was added to either human or rabbit plasminogen prior to addition of a molar equivalent of streptokinase, reactive complexes were formed in each case which consisted of human or rabbit plasminogen and native streptokinase. Upon treatment of human plasmin with a molar equivalent of streptokinase, a complex is formed which consists of altered streptokinase and human plasmin. This complex possesses the ability to activate P lasminogen is a single-chain protein of mol wt 81,000-88,000, depending on the species (Barlow et al., 1969; Sodetz et ul., 1972), and plasmin is a two-chain molecule of approximately the same molecular weight, stabilized by disulfide bond(s) (Barlow et ul., 1969;Sodetz et al., 1972). Many agents mediate the conversion of plasminogen to plasmin, among which is the bacterial endotoxin streptokinase. The mechanism of activation of human plasminogen by streptokinase has been a widely studied subject. The problem resolves itself into the manner in which the nonproteolytic protein, streptokinase, catalyzes the proteolytic cleavage required for conversion of plasminogen into plasmin. Further, the fact that not all species of plasminogen are capable of activation by streptokinase raises other interesting questions.

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“…(2) generation of the active site in plasminogen; and (3) enabling the binding and processing of substrate plasminogen molecules by the SK-PAC (Buck & Boggiano, 1971). These potential functions of SK in the SK-PAC might be ©…”

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Identification of a plasminogen binding region in streptokinase that is necessary for the creation of a functional streptokinase-plasminogen activator complex

Reed¹,

et al. 1995

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Streptokinase is a plasminogen activator widely used to treat patients with myocardial infarction. However, streptokinase is not a protease, and must first bind and interact with plasminogen to form an enzymatic complex. By measuring the binding of recombinant streptokinase fragments to plasminogen, we have sought, first, to identify a plasminogen binding region in streptokinase and, second, to explore the relation between binding (via this region) and the generation of a functional streptokinase--plasminogen activator complex. Recombinant streptokinase bound in a saturable and specific manner to human Glu-plasminogen with a dissociation constant of 4.2 x 10(-10) M. Recombinant streptokinase fragments spanning amino acids 1-127 and 1-253 could not be shown to bind to Glu-plasminogen, whereas fragments spanning amino acids 1-352, 120-352, and 244-414 bound tightly to plasminogen and each fragment completely inhibited the binding of full-length streptokinase to plasminogen. Although these latter streptokinase fragments formed a complex with plasminogen, enzymatic assays indicated that none of them was capable of generating an active site. When the streptokinase region shared by these three fragments, spanning residues 244-352, was expressed, it also bound plasminogen and competitively inhibited the formation of a functional plasminogen activator complex by full-length streptokinase. Taken together, these data indicate that streptokinase binds to plasminogen with high affinity, that a primary binding region for plasminogen is located within amino acids 244-352, and that binding via this region is necessary for the generation of a functional plasminogen activator complex.

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Interaction of Streptokinase and Human Plasminogen

Cited by 20 publications

References 25 publications

Mutation of Lysines in a Plasminogen Binding Region of Streptokinase Identifies Residues Important for Generating a Functional Activator Complex

Mutation of Lysines in a Plasminogen Binding Region of Streptokinase Identifies Residues Important for Generating a Functional Activator Complex

Interaction of streptokinase and rabbit plasminogen

Identification of a plasminogen binding region in streptokinase that is necessary for the creation of a functional streptokinase-plasminogen activator complex

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