Phosphorylation disrupts the central helix in Op18/stathmin and suppresses binding to tubulin.
Protein phosphorylation represents a ubiquitous control mechanism in living cells. The structural prerequisites and consequences of this important post-translational modification, however, are poorly understood. Oncoprotein 18/stathmin (Op18) is a globally disordered phosphoprotein that is involved in the regulation of the microtubule (MT) filament system. Here we document that phosphorylation of Ser63, which is located within a helix initiation site in Op18, disrupts the transiently formed amphipathic helix. The phosphoryl group reduces tubulin binding 10-fold and suppresses the MT polymerization inhibition activity of Op18's C-terminal domain. Op18 represents an example where phosphorylation occurs within a regular secondary structural element. Together, our findings have implications for the prediction of phosphorylation sites and give insights into the molecular behavior of a globally disordered protein.
Steinmetz
M O
MO
2Functional Genomics Area, 1Core Technology Area and 3Oncology Research, Novartis Pharma AG, CH-4002 Basel, Switzerland. michel.steinmetz@psi.ch
Jahnke
W
W
Towbin
H
H
García-Echeverría
C
C
Voshol
H
H
Müller
D
D
van Oostrum
J
J
D002942:Circular Dichroism; D004305:Dose-Response Relationship, Drug; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007477:Ions; D009682:Magnetic Resonance Spectroscopy; D008868:Microtubule Proteins; D008870:Microtubules / Q000737:chemistry; D008958:Models, Molecular; D010750:Phosphoproteins / Q000737:chemistry* / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D050777:Stathmin; D020349:Surface Plasmon Resonance; D013696:Temperature; D014404:Tubulin / Q000737:chemistry* / Q000378:metabolism
D007477:Ions; D008868:Microtubule Proteins; D010750:Phosphoproteins; D011994:Recombinant Proteins; C493995:STMN1 protein, human; D050777:Stathmin; D014404:Tubulin