Crystal structure of the atypical protein kinase domain of a TRP channel with phosphotransferase activity

Transient receptor potential (TRP) channels modulate calcium levels in euka ryotic cells in response to external signals. A novel transient receptor po tential channel has the ability to phosphorylate itself and other proteins on serine and threonine residues. The catalytic domain of this channel kina se has no detectable sequence similarity to classical eukaryotic protein ki nases and is essential for channel function. The structure of the kinase do main, reported here, reveals unexpected similarity to eukaryotic protein ki nases in the catalytic core as well as to metabolic enzymes with ATP-grasp domains. The inclusion of the channel kinase catalytic domain within the eu karyotic protein kinase superfamily indicates a significantly wider distrib ution for this group of signaling proteins than suggested previously by seq uence comparisons alone.