MAPKAPK5, A NOVEL MITOGEN-ACTIVATED PROTEIN-KINASE (MAPK)-ACTIVATED PROTEIN-KINASE, IS A SUBSTRATE OF THE EXTRACELLULAR-REGULATED KINASE (ERK) AND P38 KINASE

A novel protein kinase that has significant sequence homology to mitog en-activated protein kinase (MAPK)-activated protein kinase (MAPKAPK) was identified. This novel protein kinase has a nucleotide sequence th at encodes a protein of 473 amino acids and shares 45%, 46%, and 44% a mino acid sequence identities to MAPKAPK2, 3 and 4 respectively. North ern blot analysis revealed that it has a wide tissue distribution. Thi s novel protein kinase designated MAPKAPK5 can be phosphorylated by ex tracellular-regulated kinase (ERK), and p38 kinase but not by c-jun N- terminal kinase (JNK) in vitro. Recombinant GST-MAPKAPK5 protein can p hosphorylate a peptide derived from the regulatory light chain of myos in II. Phosphorylation of MAPKAPK5 by ERK and p38 kinase increased its activity by 9 and 15 fold respectively. Taken together, these data su ggest that MAPKAPK5 is a novel in vitro substrate for ERK and p38 kina se. (C) 1998 Academic Press.