Direct Visualization of Protease Action on Collagen Triple Helical Structure

Enzymatic processing of extracellular matrix (ECM) macromolecules by matrix metalloproteases (MMPs) is crucial in mediating physiological and pathological cell processes. However, the molecular mechanisms leading to effective physiological enzyme-ECM interactions remain elusive. Only scant information is available on the mode by which matrix proteases degrade ECM substrates. An example is the enzymatic degradation of triple helical collagen II fragments, generated by the collagenase MMP-8 cleavage, during the course of acute inflammatory conditions by gelatinase B/MMP-9. As is the case for many other matrix proteases, it is not clear how MMP-9 recognizes, binds and digests collagen in this important physiological process. We used single molecule imaging to directly visualize this protease during its interaction with collagen fragments. We show that the initial binding is mediated by the diffusion of the protease along the ordered helix on the collagen ¾ fragment, with preferential binding of the collagen tail. As the reaction progressed and prior to collagen degradation, gelatin-like morphologies resulting from the denaturation of the triple helical collagen were observed. Remarkably, this activity was independent of enzyme proteolysis and was accompanied by significant conformational changes of the working protease. Here we provide the first direct visualization of highly complex mechanisms of macromolecular interactions governing the enzymatic processing of ECM substrates by physiological protease

Minimalism

A reappraisal of Minimalism from a contemporary perspective, this book documents the careers of its leading figures as well as the practices of other associated artists. Meyer surveys its development within a broad historical and cultural context, defining Minimalism as a debate rather than a movement. Reproductions of the most significant Minimal art works, exhibitions, and contemporaries’ work are included, along with the key critical texts, artists’ statements, reviews and commentary on the movement. 330 bibl. ref. Biographical notes. Bibl. 3 p. Index of names and artworks, 5 p

Toward The Elimination Of Bias In Pediatric Research

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