The incorporation of 2'-fluoro- and 2'-aminonucleotides into a hammerhead ribozyme was accomplished by automated chemical synthesis. The presence of 2'-fluorouridines, 2'-fluorocytidines, or 2'-aminouridines did not appreciably decrease catalytic efficiency. Incorporation of 2'-aminocytidines decreased ribozyme activity approximately by a factor of 20. The replacement of all adenosines with 2'-fluoroadenosines abolished catalysis in the presence of MgCl2 within the limits of detection, but some activity was retained in the presence of MnCl2. This effect on catalysis was localized to a specific group of adenines within the conserved single-stranded region of the ribozyme. The decrease in catalytic efficiency was caused by a decrease in the rate constant; the Michaelis constant was unaltered. The 2'-fluoro and 2'-amino modifications conferred resistance toward ribonuclease degradation. Ribozymes containing 2'-fluoro- or 2'-aminonucleotides at all uridine and cytidine positions were stabilized against degradation in rabbit serum by a factor of at least 10(3) compared to unmodified ribozyme.

unc-13 mutants in Caenorhabditis elegans are characterized by a severe deficit in neurotransmitter release. Their phenotype is similar to that of the C. elegans unc-18 mutation, which is thought to affect synaptic vesicle docking to the active zone. This suggests a crucial role for the unc-13 gene product in the mediation or regulation of synaptic vesicle exocytosis. Munc13-1 is one of three closely related rat homologues of unc-13. Based on the high degree of similarity between unc-13 and Munc13 proteins, it is thought that their essential function has been conserved from C. elegans to mammals. Munc13-1 is a brain-specific peripheral membrane protein with multiple regulatory domains that may mediate diacylglycerol, phospholipid, and calcium binding. In the present study, we demonstrate by three independent methods that the C terminus of Munc13-1 interacts directly with a putative coiled coil domain in the N-terminal part of syntaxin. Syntaxin is a component of the exocytotic synaptic core complex, a heterotrimeric protein complex with an essential role in transmitter release. Through this interaction, Munc13-1 binds to a subpopulation of the exocytotic core complex containing synaptobrevin, SNAP25 (synaptosomal-associated protein of 25 kDa), and syntaxin, but to no other tested syntaxin-interacting or core complex-interacting protein. The site of interaction in syntaxin is similar to the binding site for the unc-18 homologue Munc18, but different from that of all other known syntaxin interactors. These data indicate that unc-13-related proteins may indeed be involved in the mediation or regulation of synaptic vesicle exocytosis by modulating or regulating core complex formation. The similarity between the unc-13 and unc-18 phenotypes is paralleled by the coincidence of the binding sites for Munc13-1 and Munc18 in syntaxin. It is possible that the phenotype of unc-13 and unc-18 mutations is caused by the inability of the respective mutated gene products to bind to syntaxin.Nerve cells store neurotransmitters in synaptic vesicles. These vesicles dock to a specialized region of the synaptic plasma membrane, the active zone, where they undergo a maturation or priming process. Upon depolarization and a consequential rise in the intracellular calcium concentration, primed vesicles release their content by exocytosis. Following release, vesicular membrane and protein components are retrieved by endocytosis and recycled through an early endosomal compartment. From there, synaptic vesicles bud off for a new round of regulated exocytosis (1, 2).During the last decade, the molecular mechanisms underlying synaptic vesicle exocytosis and recycling have been the focus of numerous studies. In particular, the components of the exocytotic synaptic core complex, the synaptic vesicle protein synaptobrevin and the plasma membrane proteins syntaxin and SNAP25, 1 have been analyzed in detail. These proteins are absolutely essential for neurotransmitter release, and their complex formation was originally thought to mediate the vesicl...

Oligodeoxynucleotides have been prepared that contain changes in the functional group pattern present in the EcoRI recognition site. These changes involve "functional group deletions", "functional group reversals", and "displaced functional groups". Steady-state kinetic parameters have been used to characterize the interaction of these modified recognition sites with the EcoRI endonuclease. Changes in the functional group pattern have varying effects upon the cleavage reaction. Both the exocyclic amino groups of the two adenine residues and the methyl groups of the thymine residues appear to interact with the endonuclease quite differently. In both cases efficient catalysis was observed when these functional groups were present at the "outer" dA-dT base pair. Selectivity was decreased by over an order of magnitude largely via increases in Km when these functional groups were deleted. Similar modifications at the "inner" dA-dT base pair did not alter the kinetic parameters significantly from those observed with the native sequence. Addition of an amino group to the minor groove at the outer dA-dT base pair resulted in a modified recognition site that interacted with the enzyme, on the basis of observed competitive inhibition kinetics, but was not cleaved.

The PGAS allows identification of marker-associated clinical/biological traits. Current cognitive performance in schizophrenic patients is modified by CPLX2 variants modulating posttranscriptional gene expression.