Amino-acid sequence of activation cleavage site in plasminogen: homology with "pro" part of prothrombin.

Abstract

A 38-residue fragment is isolated from carboxymethylated plasminogen. have the same sequence as the amino-terminal end of the light chain of plasmin. The sequence 1-28 is therefore the sequence of the carboxyl-terminal end of the heavy chain and contains the specific sequence at which urokinase (EC 3.4.99.26) and other plasminogen-activating serine proteases split. Two of the five carboxymethyl-cysteine residues in the isolated fragment are situated close to the cleavage site and the fragment is not itself a substrate for plasminogen-activators. Residues 1-11 show extensive sequence homology with residues 137-147 and 242-252 in rot rombin, which are located in corresponding regions of the two internally homologous 83-residue structures in the non-thrombin part of the molecule, indicating that such structures may be a common feature of the non-protease part of the larger serine protease zymogens. The determination of the complete primary structure of prothrombin (1, 2) has led to the realization that the activation catalyzed by Factor Xa (prothrombinase, EC 3.4.21.6) involves the cleavage of only two peptide bonds, namely Arg274-Thr and Arg23-Ile. Prothrombin also contains a single thrombin-sensitive bond (Argl'6-Ser). The two FactorXa-sensitive bonds are preceded by the identical tetrapeptide sequences -Ile271-Glu-Gly-Arg-and Ile320-Glu-Gly-Arg, whereas the corresponding residues at the thrombin-sensitive site are different, namely -Vall'3-I1e-Pro-Arg. These findings indicated that a specific oligopeptide sequence immediately preceding the bond to be cleaved is required to define a particular protein as being a substrate for one of those highly specific trypsin-like serine proteases, such as Factors Xa, IXa, XIa, XIIa of the blood coagulation system, urokinase (EC 3.4.99.26) and others of the fibrinolytic system, kallikrein, and the proteolytic components of the complement system, which are involved in the activation and control of many extracellularly regulated processes. To test this possibility with respect to Factor Xa specificity we recently synthesized the compound Tos-LIle-LGlu-Gly-LArgp-nitroanilide and found it to be a good substrate for Factor Xa, but not for thrombin (EC 3.4.21.5), plasmin (EC 3.4.21.7), urokinase or streptokinase-plasminogen complex (T. E. Petersen, L. Sottrup-Jensen, and S. Magnusson, in preparation). The rate of Factor-Xa-catalyzed cleavage of this synthetic compound could not by itself explain the rapid rate of activation of prothrombin. One possible explanation for this is that the two -Ile-Glu-Gly-Arg-sequences may be

Structure and function of microplasminogen: II. Determinants of activation by urokinase and by the bacterial activator streptokinase

“…We have prepared and studied a series of mutant mflgs with the above questions in mind and were attentive to the unusual disulfide structures in the vicinity of the activation site (Summaria et al, 1967;Sottrup-Jensen et al, 1975) (Fig. I).…”

Purification and Characterization of a Melanoma Cell Plasminogen Activator

“…Comparisons of the A and B sequences with plasmin [20], thrombin [21] and other proteases reveal that the B chain is clearly homologous to the N-terminal sequence of the catalytically active chain of activated serine proteases. This is shown in Table 4.…”

Haemophilus influenzae Uses the Surface Protein E To Acquire Human Plasminogen and To Evade Innate Immunity

“…This coagulation regulator is composed of an N-terminal preactivation peptide, five consecutive disulfide-bounded kringle domains (K1-K5), followed by a serine protease domain (1)(2)(3). Plasminogen, which has a plasma concentration of ∼200 mg/ml, is synthesized and secreted by liver cells and is also present in extracellular body fluids (4).…”