FAST
FAST kinase family members, FASTK and FASTKD1 through FASTKD5, are mitochondrial proteins grouped among atypical kinases though their established activities center on organellar RNA metabolism rather than protein phosphorylation. FASTKD proteins share an N-terminal mitochondria-targeting MIT-like domain, central RAP1/RAP2 RNA-processing modules, and a C-terminal domain; they process and stabilize mitochondrial mRNAs at non-canonical transcript junctions, supporting oxidative-phosphorylation gene expression, and FASTKD2 additionally participates in apoptosis-linked outer-membrane remodeling. FASTK itself was first identified in Fas-mediated apoptotic signaling. Loss of FASTKD function impairs respiratory-chain assembly and has been linked to mitochondrial disease phenotypes. Recombinant FAST family proteins serve mitochondrial RNA-processing reconstitution, apoptosis, and bioenergetics studies.
