Novel Inhibitors to MmpL3 Transporter of Mycobacterium tuberculosis by Structure-Based High-Throughput Virtual Screening and Molecular Dynamics Simulations.

Tuberculosis (TB)-causing bacterium Mycobacterium tuberculosis (Mtb) utilizes mycolic acids for building the mycobacterial cell wall, which is critical in providing defense against external factors and resisting antibiotic action. MmpL3 is a secondary resistance nodulation division transporter that facilitates the coupled transport of mycolic acid precursor into the periplasm using the proton motive force, thus making it an attractive drug target for TB infection. In 2019, X-ray crystal structures of MmpL3 from M. smegmatis were solved with a promising inhibitor SQ109, which showed promise against drug-resistant TB in Phase II clinical trials. Still, there is a pressing need to discover more effective MmpL3 inhibitors to counteract rising antibiotic resistance. In this study, structure-based high-throughput virtual screening combined with molecular dynamics (MD) simulations identified potential novel MmpL3 inhibitors. Approximately 17 million compounds from the ZINC15 database were screened against the SQ109 binding site on the MmpL3 protein using drug property filters and glide XP docking scores. From this, the top nine compounds and the MmpL3-SQ109 crystal complex structure each underwent 2 × 200 ns MD simulations to probe the inhibitor binding energetics to MmpL3. Four of the nine compounds exhibited stable binding properties and favorable drug properties, suggesting these four compounds could be potential novel inhibitors of MmpL3 for M. tuberculosis.

Inhibition Mechanism of Anti-TB Drug SQ109: Allosteric Inhibition of TMM Translocation of Mycobacterium Tuberculosis MmpL3 Transporter.

The mycolic acid transporter MmpL3 is driven by proton motive forces (PMF) and functions via an antiport mechanism. Although the crystal structures of the Mycobacterium smegmatis MmpL3 transporter alone and in complex with a trehalose monomycolate (TMM) substrate and an antituberculosis drug candidate SQ109 under Phase 2b-3 Clinical Trials are available, no water and no conformational change in MmpL3 were observed in these structures to explain SQ109's inhibition mechanism of proton and TMM transportation. In this study, molecular dynamics simulations of both apo form and inhibitor-bound MmpL3 in an explicit membrane were used to decipher the inhibition mechanism of SQ109. In the apo system, the close-open motion of the two TM domains, likely driven by the proton translocation, drives the close-open motion of the two PD domains, presumably allowing for TMM translocation. In contrast, in the holo system, the two PD domains are locked in a closed state, and the two TM domains are locked in an off pathway wider open state due to the binding of the inhibitor. Consistent with the close-open motion of the two PD domains, TMM entry size changes in the apo system, likely loading and moving the TMM, but does not vary much in the holo system and probably impair the movement of the TMM. Furthermore, we observed that water molecules passed through the central channel of the MmpL3 transporter to the cytoplasmic side in the apo system but not in the holo system, with a mean passing time of ∼135 ns. Because water wires play an essential role in transporting protons, our findings shed light on the importance of PMF in driving the close-open motion of the two TM domains. Interestingly, the key channel residues involved in water passage display considerable overlap with conserved residues within the MmpL protein family, supporting their critical function role.

Informed or anxious: patient preferences for release of test results of increasing sensitivity on electronic patient portals.

Worldwide, governments and healthcare systems are moving towards increased transparency to improve care quality, increase patient engagement, and decrease costs. For example, the American 21st Century Cures Act Final Rule requires providers to grant patients access to their electronic medical record. Unfortunately, limited research guides release of test results to online patient portals, especially concerning emotionally sensitive information. To address this gap, we surveyed the largest patient sample published to date. This cross-sectional survey project was conducted by the Market Research & Insights and Office of Patient Experience departments at a large academic medical center. Data were analyzed in SPSS using descriptive statistics and Z-tests. Of 8030 respondents, 74% and 57% accepted first learning their results online for cholesterol and strep throat tests, respectively. Most prefer in-person appointments for more serious tests detecting cancer (54%) and fetal miscarriage (53%). Excluding sexually transmitted disease (STD) testing, there are no clinically significant differences in preference between respondents previously diagnosed with the condition in question and respondents without such experience. When weighing the possibility of a 3-week wait to hear from their provider, most patients want automatic release of cholesterol (94%), strep throat (90%), genetic (68%), and STD (60%) test results, but the majority say it is unacceptable to receive Alzheimer's (52%), fetal miscarriage (51%), and cancer (59%) test results this way. Electronic results release is acceptable for less serious tests, but not for more consequential tests. Providers should consider patient preferences when developing policies to increase healthcare transparency. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12553-021-00628-5.