Inhibitory Effects of Novel Immucillin Analogues on \u3ci\u3eBorrelia burgdorferi\u3c/i\u3e Bgp Nucleosidase

The pathogenic spirochaete Borrelia burgdorferi causes Lyme disease and is transmitted by deer ticks when they feed. Lyme disease is multisystemic—it adversely affects the heart, joints, and skin. Recent studies demonstrate that B. burgdorferi possesses three methylthioadenosine/Sadenosylhomocysteine (MTA/SAH) nucleosidases essential for the catabolic breakdown of both MTA and SAH. Both MTA and SAH are by-products of major pathways involving Sadenosylmethionine (SAM) and are kept at low micromolar concentrations due to their inhibitory activity. This project examined the effect of transition state inhibitors on the surface binding Borrelia glycosaminoglycanbinding protein (Bgp) nucleosidase using recombinant Bgp and whole-cell B. burgdorferi activity assays. The transition state analogues are potent inhibitors of Bgp activity with Ki values ranging from 6pM-6nM. Bgp on the surface of live B. burgdorferi was also inhibited by treatment with low nanomolar concentrations of transition state analogues

Structural Basis for α-Conotoxin Potency and Selectivity

Parkinson\u27s disease is a debilitating movement disorder characterized by altered levels of α6β2* nicotinic acetylcholine receptors (nAChRs) localized on presynaptic striatal catecholaminergic neurons. α-Conotoxin MII (α-CTx MII) is a highly useful ligand to probe α6ß2 nAChRs structure and function, but it does not discriminate among closely related α6* nAChR subtypes. Modification of the α-CTx MII primary sequence led to the identification of α-CTx MII[E11A], an analog with 500-5300 fold discrimination between α6* subtypes found in both human and non-human primates. α-CTx MII[E11A] binds most strongly (femtomolar dissociation constant) to the high affinity α6* nAChR, a subtype that is selectively lost in Parkinson\u27s disease. Here we present the three-dimensional solution structure for α-CTx MII[E11A] as determined by two-dimensional 1H NMR spectroscopy to 0.13 +/- 0.09 Ǻ backbone and 0.45 +/- 0.08 Ǻ heavy atom root mean square deviation from mean structure. Structural comparisons suggest that the increased hydrophobic area of α-CTx MII[E11A] relative to other members of the α-CTx family may be responsible for its exceptionally high affinity for α6α4β2* nAChR as well as discrimination between α6ß2 and α3β2 containing nAChRs. This finding may enable the rational design of novel peptide analogs that demonstrate enhanced specificity for α6* nAChR subunit interfaces and provide a means to better understand nAChR structural determinants that modulate brain dopamine levels and the pathophysiology of Parkinson\u27s disease