Kinase at the outer chloroplast membrane 1 (KOC1)

KOC1 (Kinase at the outer chloroplast membrane 1) is an integral membrane kinase residing at the outer envelope of chloroplasts in *Arabidopsis*. It stably associates with the translocon at the outer chloroplast membrane (TOC) complex and is localized specifically to the chloroplast periphery. KOC1 phosphorylates the acidic N-terminal domains of TOC159 and its homologs TOC120 and TOC132, which are import receptors for nuclear-encoded preproteins. This phosphorylation is required for efficient preprotein import into chloroplasts, facilitating rapid chloroplast biogenesis, especially during transitions such as seedling de-etiolation. KOC1 has a kinase domain, a HERC2-related region, and a single transmembrane helix, but lacks the RING and ankyrin motifs found in its closest homolog, the KEG (Keep On Going) protein. Loss of KOC1 results in reduced protein import efficiency and diminished chloroplast biogenesis under certain conditions, but does not alter the abundance of TOC/TIC complex components under normal growth.

Other names

Regulatory kinase at the outer chloroplast membrane 1KOC1