Background: Cocaine interaction with DAT was assessed using the irreversible binding cocaine analog RTI 82. Results: Molecular modeling and peptide mapping identify adduction of RTI 82 to Phe-319 and Phe-320 of rat DAT and human DAT, respectively. Conclusion: Tropane-based pharmacophores bind to DAT in the central substrate site. Significance: Mapping the cocaine-binding site reveals new insights for medication discovery.

The genome of Bacillus subtilis strain 168 contains the mother cell metabolic gene (mmg) operon that encodes homologues from the methylcitric acid cycle. We showed that the three genes, mmgDE and yqiQ(mmgF), provide three of the five steps of the methylcitric acid cycle. We also showed that the fourth step can be supplied by citB (aconitase), and we suggest that the fifth missing step, the propionyl-CoA synthetase, is probably skipped because the β-oxidation of methyl-branched fatty acids by the enzymes encoded by mmgABC should produce propionyl-CoA. We also noted interesting enzymology for MmgD and MmgE. First, MmgD is a bifunctional citrate synthase/2-methylcitrate synthase with 2.3-fold higher activity as a 2-methylcitrate synthase. This enzyme catalyzes the formation of either (2S,3R)- or (2R,3S)-2-methylcitrate, but reports of 2-methylcitrate synthases from other species indicated that they produced the (2S,3S) isomer. However, we showed that MmgD and PrpC (from Escherichia coli) in fact produce the same stereoisomer. Second, the MmgE enzyme is not a stereospecific 2-methylcitrate dehydratase because it can dehydrate at least two of the four diastereomers of 2-methylcitrate to yield either (E)-2-methylaconitate or (Z)-2-methylaconitate. We also showed for the first time that the E. coli homologue PrpD exhibited the same lack of stereospecificity. However, the physiological pathways proceed via (Z)-2-methylaconitate, which served as the substrate for the citB enzyme in the synthesis of 2-methylisocitrate. We completed our characterization of this pathway by showing that the 2-methylisocitrate produced by CitB is converted to pyruvate and succinate by the enzyme YqiQ(MmgF).

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Drug overdose remains a leading cause of death in the US, and the majority of opioid overdose fatalities involve fentanyl. This study aims to measure the degree of concordance between self-reported and biologically tested exposure to fentanyl. We conducted a cross-sectional analysis using survey and urinalysis data collected between 2019 and 2020 from Anne Arundel County, Maryland. Among urinalysis participants (n =113), 30% reported daily fentanyl use, and among this group, only 54% had a fentanyl-positive result. Cohen Kappa between self-reported and biologically detected fentanyl use was 0.26, indicating minimal agreement between the 2 markers. Limitations to interpreting self-reported and urinalysis data are discussed in this report.

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