Biology subjects

Mehta, V.

Publications and source records attributed to Mehta, V..

2 recordsLinked to original sources

bioRxiv2021

Structure of Mycobacterium tuberculosis Cya, an evolutionary ancestor of the mammalian membrane adenylyl cyclases

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 [A] 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 SummaryStructure of M. tuberculosis membrane adenylyl cyclase Cya

biochemistry↗

bioRxiv2021

Structural basis of adenylyl cyclase 9 activation

Adenylyl cyclase 9 (AC9) is a membrane-bound enzyme that converts ATP into cAMP. The enzyme is weakly activated by forskolin, fully activated by the G protein Gs subunit and is autoinhibited by the AC9 C-terminus. Although our recent structural studies of the AC9-Gs complex provided the framework for understanding AC9 autoinhibition, the conformational changes that AC9 undergoes in response to activator binding remains poorly understood. Here, we present the cryo-EM structures of AC9 in several distinct states: (i) AC9 bound to a nucleotide inhibitor MANT-GTP, (ii) bound to an artificial activator (DARPin C4) and MANT-GTP, (iii) bound to DARPin C4 and a nucleotide analogue ATPS, (iv) bound to Gs and MANT-GTP. The artificial activator DARPin C4 partially activates AC9 by binding at a site that overlaps with the Gs binding site. Together with the previously observed occluded and forskolin-bound conformations, structural comparisons of AC9 in the four new conformations show that secondary structure rearrangements in the region surrounding the forskolin binding site are essential for AC9 activation. One Sentence SummaryCryo-EM reveals activator-induced conformational changes in adenylyl cyclase AC9

biochemistry↗