IDENTIFICATION OF THE MAJOR AUTOPHOSPHORYLATION SITES OF NYK MER, AN NCAM-RELATED RECEPTOR TYROSINE KINASE/

LING L TEMPLETON D KUNG HJ

L. Ling et al., IDENTIFICATION OF THE MAJOR AUTOPHOSPHORYLATION SITES OF NYK MER, AN NCAM-RELATED RECEPTOR TYROSINE KINASE/, The Journal of biological chemistry, 271(31), 1996, pp. 18355-18362

49

INGLESE

Article

Biology

The Journal of biological chemistry → ACNP

0021-9258

271

31

1996

18355 - 18362

ISI

0021-9258(1996)271:31<18355:IOTMAS>2.0.ZU;2-5

Nyk/Mer receptor tyrosine kinase is a new member of the Ufo/Axl tyrosi ne kinase family and is characterized by its neural cell adhesion mole cule-like extracellular domain, By using a vaccinia virus expression s ystem to express a constitutively activated form of Nyk, we identified the major sites of Nyk autophosphorylation in tryptic peptide IY(749) SGDY(753)Y(754)R. Tyr-749, Tyr-753, and Tyr-754 in this peptide lie in the activation loop of the kinase domain, We also studied a series of Nyk mutants in which the three tyrosine residues were replaced indivi dually, in pairs, or all together by phenylalanine. Single mutations o f Tyr 749 or Tyr-753 to phenylalanine reduced Nyk kinase activity towa rd exogenous substrate to 39 or 10% of that of the wild type Nyk, resp ectively, whereas the Tyr-754 mutant is completely inactive, All of th e double and triple Tyr-Phe mutants reduced Nyk kinase activity to a l evel below the background, Similar results were obtained when Nyk auto phosphorylation levels were examined, Our studies suggest that full ac tivity of Nyk/Mer kinase requires phosphorylation of all three tyrosin e residues in the kinase domain (Tyr-749, Tyr-753, and Tyr-754) and th at Nyk kinase activity is modulated by the level of autophosphorylatio n in the kinase domain, Given the highly conserved nature of this regi on among the Ufo/Axl receptor family members, the information presente d in this report may provide insight to the biochemical properties of other members of this family.