Journal
EMBO JOURNAL
Volume 25, Issue 19, Pages 4686-4696Publisher
NATURE PUBLISHING GROUP
DOI: 10.1038/sj.emboj.7601315
Keywords
activation mechanism; crystal structure; Eph receptor tyrosine kinase; NMR spectroscopy
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Eph receptor tyrosine kinases (RTKs) mediate numerous developmental processes. Their activity is regulated by auto- phosphorylation on two tyrosines within the juxta-membrane segment (JMS) immediately N-terminal to the kinase domain (KD). Here, we probe the molecular details of Eph kinase activation through mutational analysis, X-ray crystallography and NMR spectroscopy on auto-inhibited and active EphB2 and EphA4 fragments. We show that a Tyr750Ala gain-of-function mutation in the KD and JMS phosphorylation independently induce disorder of the JMS and its dissociation from the KD. Our X-ray analyses demonstrate that this occurs without major conformational changes to the KD and with only partial ordering of the KD activation segment. However, conformational exchange for helix alpha C in the N-terminal KD lobe and for the activation segment, coupled with increased inter-lobe dynamics, is observed upon kinase activation in our NMR analyses. Overall, our results suggest that a change in inter-lobe dynamics and the sampling of catalytically competent conformations for helix aC and the activation segment rather than a transition to a static active conformation underlies Eph RTK activation.
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