Molecular Probes

Collagen is the major structural scaffold in the body and serves as barrier between tissues, and thus its turnover is tightly regulated. Collagen triple-helical structure renders it resistant to general proteolysis. Several proteases are capable of cleaving the triplehelical regions of collagen, including several mammalian matrix metalloproteinases (MMPs) and bacterial collagenases. MMP-mediated collagenolysis is associated with numerous diseases and some bacterial collagenases have found clinical application use due to their efficiency in the hydrolysis of the collagen triple-helix. A selective Förster resonance energy transfer triple-helical peptide (fTHP) probe for monitoring the activity of Clostridial collagenase has been developed. The fTHP [sequence: Gly-mep-Flp-(Glyvi Pro-Hyp)4-Gly-Lys(Mca)-Thr-Gly-Pro-Leu-Gly-Pro-Pro-Gly-Lys(Dnp)-Ser-(Gly-Pro-Hyp)4-NH2] was stable at 37 °C and was efficiently hydrolyzed by bacterial collagenase (kcat/KM = 25,000 s -1 M-1) but not by clostripain, trypsin, neutral protease, thermolysin, or elastase. The bacterial collagenase fTHP assay can be utilized in applications where specific activity towards triple-helical collagen needs to be evaluated, such as isolation of cells from various tissues. An fTHP scaffold was also utilized to evaluate the sequence preferences of eight MMPs. Residues spanning from P3 to P11 investigated using a positional scanning synthetic combinatorial library. Deconvolution of the library data revealed distinct motifs for several MMPs and discrimination among closely related MMPs. The results of this study show that the P10 11 substrate play an important role in the collagenase-substrate interactions and that modifying these residues can drastically affect the affinity of MMPs towards THP substrates. The identified sequence preferences of MMPs will enable the design of selective triple-helical MMP probes that could be used for monitoring in vivo enzyme activity and enzyme-facilitated drug delivery.

Conotoxins are peptides expressed by the exogenome of more than 800 species of marine mollusks belonging to the genus Conus (cone snails.) Owing to their high specificity and affinity for ion channels, transporter molecules, and cell receptors of the central and peripheral nervous systems, conotoxins have been investigated for nearly four decades. These efforts on conotoxin research made possible the FDA approved use of Ziconitide/Prialt, a conotoxin derived from the venom of Conus magus, which effectively treats patients suffering from severe chronic pain without consequent narcotic effects. Additionally, six other conotoxins have reached clinical trials and many novel ones are being discovered every day. Investigations reported in this dissertation broadens the applicability of conotoxins to non-excitable systems. Here, conotoxins from the dissected venom of the vermivorous cone snail Conus nux were isolated and purified by size exclusion and reverse phase HPLC and characterized by MALDI-TOF and MS/MS spectrometry. The purified conopeptide fractions revealed: 1) antagonist activity of conotoxin NuxVID on two human voltage-gated sodium channels, displaying capabilities as a practical molecular probe and a potential therapeutic lead. 2) Ability for two novel conotoxins to traverse artificial biological membranes, suggesting their potential as drug delivery systems. 3) In vitro capacity of several novel conopeptides to interfere with the adhesion of PfEMP1 domains, expressed in P. falciparum infected erythrocytes, to vascular endothelial and placenta receptors. Lastly, this work reveals binding of the synthetic form of α-conotoxin ImI, from the vermivorous cone snail Conus imperialis, to the α7 nAChR of macrophage-like-cells derived from the pre-monocytic leukemic cell line THP-1 in support of the involvement of this receptor in the cholinergic anti-inflammatory pathway.