Khalid Anwar, Faizan Ahmad, Md. Imtaiyaz Hassan
Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia (Central University), Jamia Nagar, New Delhi 110 025, India.
MAP (Mitogen Activated Protein) kinase-interacting serine/threonine-protein kinase 1 (Mknk1 or Mnk1) is an important intermediate member of the oncogene expression cascade pathway and its inactivation proved to be delay in tumerigenesis. Mnk1 is a member of calmodulin-dependent kinase (CamK) of the MAPKKAPK serine/threonine family that can regulate translation. Following activation by MAP kinases, Mnk1 phosphorylates eIF4E at Ser209, increasing its affinity for the 7-methylguanosine-containing mRNA cap. Two MAPK Threonine phosphorylation sites are essential for its kinase activity. Two isoforms (Mnk1a & Mnk1b) are found in human having similar structure and function. The protein consists of 465 amino acid residues (51, 342 Da) with pI value of 6.26. The protein is cytoplasmic as well as nucleoplasmic. Domain containing 49 to 374 residues governs the kinase activity. All Mnk have NLS (Nuclear Localization Signal) at the N-terminus region as well as CRM I motif at C-terminus meant for nuclear export. The proton acceptor active site is at Asp211. The ATP-binding position was found to at Lys78. The protein structure is predominately α-helical. Sequence analysis suggests that mutations at Lys78 to Met, Glu232 to Ala), Thr250 Ala) & Thr255 to Ala results into protein kinase inactivation. Read More …