The YHS-Domain of an Adenylyl Cyclase from Mycobacterium phlei Is a Probable Copper-Sensor Module

YHS-domains are small protein modules which have been proposed to bind transition-metal ions like the related TRASH-domains. They are found in a variety of enzymes including copper-transporting ATPases and adenylyl cyclases. Here we investigate a class IIIc adenylyl cyclase from Mycobacterium phlei which contains a C-terminal YHS-domain linked to the catalytic domain by a peptide of 8 amino acids. We expressed the isolated catalytic domain and the full-length enzyme in E. coli. The catalytic domain requires millimolar Mn(2+) as a cofactor for efficient production of cAMP, is unaffected by low micromolar concentrations of Cu(2+) and inhibited by concentrations higher than 10 μM. The full-length enzyme also requires Mn(2+) in the absence of an activator. However, 1–10 μM Cu(2+) stimulate the M. phlei adenylyl cyclase sixfold when assayed with Mn(2+). With Mg(2+) as the probable physiological cofactor of the adenylyl cyclase Cu(2+) specifically switches the enzyme from an inactive to an active state. Other transition-metal ions do not elicit activity with Mg(2+). We favor the view that the YHS-domain of M. phlei adenylyl cyclase acts as a sensor for copper ions and signals elevated levels of the transition-metal via cAMP. By analogy to TRASH-domains binding of Cu(2+) probably occurs via one conserved aspartate and three conserved cysteine-residues in the YHS-domain.