The Structure of a pH-Sensing Mycobacterial Adenylyl Cyclase Holoenzyme

Abstract

Class III adenylyl cyclases contain catalytic and regulatory domains, yet structural insight into their interactions is missing. We show that the mycobacterial adenylyl cyclase Rv1264 is rendered a pH sensor by its N-terminal domain. In the structure of the inhibited state, catalytic and regulatory domains share a large interface involving catalytic residues. In the structure of the active state, the two catalytic domains rotate by 55 degrees to form two catalytic sites at their interface. Two alpha helices serve as molecular switches. Mutagenesis is consistent with a regulatory role of the structural transition, and we suggest that the transition is regulated by pH.

PAS-mediated Dimerization of Soluble Guanylyl Cyclase Revealed by Signal Transduction Histidine Kinase Domain Crystal Structure

“…4A), suggestive of a similar dimerization function in sGC. The hydrophobic nature of all 5 residues comprising the central cluster of the dimerization interface (Leu 8 , Leu 13 , Phe 17 , Phe 100 , and Leu 102 ) is conserved as well suggesting that sGC␣1 and sGC␤1 H-NOXA domains could similarly heterodimerize, or homodimerize as observed in solution for the sGC␤1 H-NOXA domain (Fig. 4B).…”

“…deviations of 2.2 Å for the monomer superposition yet low enough to indicate a similar dimer arrangement. Their similar dimer organization is attained because the hydrophobic nature of several residues at the core of the dimer interface is conserved (Leu 13 , Phe 100 , and Leu 102 in NpSTHK correspond to Leu 26 , Leu 127 , and Leu 129 , respectively, in EcDOS; see Fig. 1B).…”

“…Structural information on sGC is limited and comes mostly from the structures of the homologous adenylyl cyclase catalytic domain (11)(12)(13) and bacterial H-NOX domains (14 -16). Even less is structurally known about the H-NOXA/CC region except that it was found to contain two distinct regions key for dimerization: one comprises H-NOXA ␤1 residues 204 -244, and the second contains CC residues 379 -408 with the intervening sequences postulated to contribute to a functional binding region (17).…”

Molecular Details of cAMP Generation in Mammalian Cells: A Tale of Two Systems

“…Activation is mediated by a helix-to-loop transition in the linker between regulatory and catalytic domains which enables a large repositioning of the two catalytic domains relative to each other as well as major conformational changes of active site regions. 56 The only other structurally characterized regulatory domain of a class III AC is the isolated GAF-region of a the cyanobacterial CyaB2 AC, 108 which could not reveal how it translates ligand binding into a change of activity of the catalytic domain. Taken together, repositioning of the two domains of the class III catalytic core appears to constitute a mechanism for regulating its activity, but a firm and detailed understanding of the regulation of mammalian AC enzymes through regulatory domains and proteins will require further structural and mechanistic studies.…”

“…The first crystal structure of a class III AC catalytic domain to be solved was a non-physiological mammalian C 2 homodimer, 53 followed by crystal structures of a mammalian C 1 C 2 heterodimer, 40,54 two trypanosomal catalytic cores, 55 several mycobacterial ACs, 41,56,57 and a cyanobacterial sAC homolog. 38 These structures confirmed the conserved architecture of class III catalytic domains (Figure 4(a)) previously suggested by their sequence similarities ( Figure 5).…”