Adaptation of plasminogen activator sequences to known protease structures

Area of Science:

• Biochemistry
• Structural Biology
• Enzymology

Background:

• Urokinase (UK) and tissue-type plasminogen activator (TPA) are serine proteases with critical roles in fibrinolysis.
• Understanding their structure-function relationships is essential for developing targeted therapies.

Purpose of the Study:

• To elucidate the structural basis of plasminogen activation specificity for UK and TPA.
• To compare their structural features with other trypsin-like serine proteases.

Main Methods:

• Sequence alignment of UK and TPA with chymotrypsin, trypsin, and elastase based on structurally conserved regions.
• Model-building of UK based on the chymotrypsin structure due to disulfide bond patterns.
• Identification of key residues involved in substrate binding and specificity.

Main Results:

• UK was structurally modeled on chymotrypsin, revealing an extra disulfide bond involving cysteines 50 and 111d.
• Surface insertions, common to UK and TPA, may play a role in plasminogen recognition.
• Specific residues (Asp 97, Lys 143, Arg 217/Leu) were identified as potentially contributing to plasminogen activating specificity.

Conclusions:

• The structural framework of UK and TPA, particularly conserved regions and disulfide patterns, influences their enzymatic activity.
• Specific amino acid variations at functional positions dictate substrate specificity and may impact inhibitor binding.
• Further investigation into these structural determinants can inform the design of selective fibrinolytic agents.