Record Details

Involvement of a nine-residue loop of streptokinase in the generation of macromolecular substrate specificity by the activator complex through interaction with substrate kringle domains.

DIR@IMTECH: CSIR-Institute of Microbial Technology

View Archive Info
 
 
Field Value
 
Title Involvement of a nine-residue loop of streptokinase in the generation of macromolecular substrate specificity by the activator complex through interaction with substrate kringle domains.
 
Creator Dhar, Jayeeta
Pande, Abhay H
Sundram, Vasudha
Nanda, Jagpreet S
Mande, Shekhar C
Sahni, Girish
 
Subject QD Chemistry
 
Description The selective deletion of a discrete surface-exposed epitope (residues 254-262; 250-loop) in the beta domain of streptokinase (SK) significantly decreased the rates of substrate human plasminogen (HPG) activation by the mutant (SK(del254-262)). A kinetic analysis of SK(del254-262) revealed that its low HPG activator activity arose from a 5-6-fold increase in K(m) for HPG as substrate, with little alteration in k(cat) rates. This increase in the K(m) for the macromolecular substrate was proportional to a similar decrease in the binding affinity for substrate HPG as observed in a new resonant mirror-based assay for the real-time kinetic analysis of the docking of substrate HPG onto preformed binary complex. In contrast, studies on the interaction of the two proteins with microplasminogen showed no difference between the rates of activation of microplasminogen under conditions where HPG was activated differentially by nSK and SK(del254-262). The involvement of kringles was further indicated by a hypersusceptibility of the SK(del254-262).plasmin activator complex to epsilon-aminocaproic acid-mediated inhibition of substrate HPG activation in comparison with that of the nSK.plasmin activator complex. Further, ternary binding experiments on the resonant mirror showed that the binding affinity of kringles 1-5 of HPG to SK(del254-262).HPG was reduced by about 3-fold in comparison with that of nSK.HPG . Overall, these observations identify the 250 loop in the beta domain of SK as an important structural determinant of the inordinately stringent substrate specificity of the SK.HPG activator complex and demonstrate that it promotes the binding of substrate HPG to the activator via the kringle(s) during the HPG activation process.
 
Publisher ASBMB
 
Date 2002-04-12
 
Type Article
PeerReviewed
 
Format application/pdf
 
Identifier http://crdd.osdd.net/open/887/1/sahni2002.pdf
Dhar, Jayeeta and Pande, Abhay H and Sundram, Vasudha and Nanda, Jagpreet S and Mande, Shekhar C and Sahni, Girish (2002) Involvement of a nine-residue loop of streptokinase in the generation of macromolecular substrate specificity by the activator complex through interaction with substrate kringle domains. The Journal of biological chemistry, 277 (15). pp. 13257-67. ISSN 0021-9258
 
Relation http://www.jbc.org/content/277/15/13257.full.pdf+html
http://crdd.osdd.net/open/887/