CtpB is a plasma membrane copper (I) transporting P-type ATPase of Mycobacterium tuberculosis

BACKGROUND: The intracellular concentration of heavy-metal cations, such as copper, nickel, and zinc is pivotal for the mycobacterial response to the hostile environment inside macrophages. To date, copper transport mediated by P-type ATPases across the mycobacterial plasma membrane has not been sufficiently explored. RESULTS: In this work, the ATPase activity of the putative Mycobacterium tuberculosis P1B-type ATPase CtpB was associated with copper (I) transport from mycobacterial cells. Although CtpB heterologously expressed in M. smegmatis induced tolerance to toxic concentrations of Cu2+ and a metal preference for Cu+, the disruption of ctpB in M. tuberculosis cells did not promote impaired cell growth or heavy-metal accumulation in whole mutant cells in cultures under high doses of copper. In addition, the Cu+ ATPase activity of CtpB embedded in the plasma mem-brane showed features of high affinity/slow turnover ATPases, with enzymatic parametersKM 0.19 ± 0.04 µM and Vmax 2.29 ± 0.10 nmol/mg min. In contrast, the ctpB gene transcription was activated in cells under culture conditions that mimicked the hostile intraphagosomal environment, such as hypoxia, nitrosative and oxidative stress, but not under high doses of copper. CONCLUSIONS: The overall results suggest that M. tuberculosis CtpB is associated with Cu+ transport from mycobacterial cells possibly playing a role different from copper detoxification.

Exploring the binding affinities of p300 enzyme activators CTPB and CTB using docking method.

CREB binding protein (CBP) and E1A binding protein p300, also known as p300 are functionally related transcriptional co-activators (CoAs) and histone acetyltransferases (HATs). Some small molecules, which target HATs can activate or inhibit the p300 enzyme potently. Here, we report the binding affinities of two small molecules CTPB [N-(4-chloro- 3-trifluoromethyl-phenyl)-2-ethoxy-6-pentadecyl-benzamide] and CTB [N-(4-chloro-3-trifluoromethyl-phenyl)-2-ethoxy-benzamide] with p300 using docking method to obtain the insight of their interaction with p300. These small molecules bind to the enzyme, subsequently causing a structural change in the enzyme, which is responsible for the HAT activation. CTB exhibits higher binding affinity than CTPB, and their lowest docked energies are -7.72, -1.18 kcal/mol, respectively. In CTPB molecule, phenolic hydroxyl of Tyr1397 interacts with the non-polar atoms C(5E) and C(5F), and forms polar-non polar interactions. Similar interactions have also been observed in CTB. The residues Tyr1446 and Cys1438 interact with the non-pentadecyl atoms. Further, the docking study predicts a N-HO hydrogen bonding interaction between CTB and Leu1398, in which the HO contact distance is 2.06 Å. The long pentadecyl chain of CTPB reduces the formation of hydrogen bond with the p300. The H-bond interaction could be the key factor for the better activation of CTB.