Abstract
Mycobacterium tuberculosis adenylyl cyclase (AC) Rv1625c / Cya is an evolutionary ancestor of the mammalian membrane ACs and a model system for studies of their structure and function. Although the vital role of ACs in cellular signaling is well established, the function of their transmembrane (TM) regions remains unknown. Here we describe the cryo-EM structure of Cya bound to a stabilizing nanobody at 3.6 Å resolution. The TM helices 1-5 form a structurally conserved domain that facilitates the assembly of the helical and catalytic domains. The TM region contains discrete pockets accessible from the extracellular and cytosolic side of the membrane. Neutralization of the negatively charged extracellular pocket Ex1 destabilizes the cytosolic helical domain and reduces the catalytic activity of the enzyme. The TM domain acts as a functional component of Cya, guiding the assembly of the catalytic domain and providing the means for direct regulation of catalytic activity in response to extracellular ligands.
One-Sentence Summary Structure of M. tuberculosis membrane adenylyl cyclase Cya
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Minor changes have been introduced to the text, including: an updated Data and materials availability statement indicating the PDB and EMDB accession codes, a corrected X-axis in Figure 5F and updated Table S1 and S2, Figures 1, S3, S6, corresponding to the latest refined and deposited models of Cya-Nb4 complex.
