Wj. Metzler et al., CHARACTERIZATION OF THE 3-DIMENSIONAL SOLUTION STRUCTURE OF HUMAN PROFILIN - H-1, C-13, AND N-15 NMR ASSIGNMENTS AND GLOBAL FOLDING PATTERN, Biochemistry, 32(50), 1993, pp. 13818-13829
Human profilin is a 15-kDa protein that plays a major role in the sign
aling pathway leading to cytoskeletal rearrangement. Essentially compl
ete assignment of the H-1, C-13, and N-15 resonances of human profilin
have been made by analysis of multidimensional, double- and triple-re
sonance nuclear magnetic resonance (NMR) experiments. The deviation of
the C-13alpha and C-13beta chemical shifts from their respective rand
om coil values were analyzed and correlate well with the secondary str
ucture determined from the NMR data. Twenty structures of human profil
in were refined in the program X-PLOR using a total of 1186 experiment
ally derived conformational restraints. The structures converged to a
root mean squared distance deviation of 1.5 angstrom for the backbone
atoms. The resultant conformational ensemble indicates that human prof
ilin is an alpha/beta protein comprised of a seven-stranded, antiparal
lel beta-sheet and three helices. The secondary structure elements for
human profilin are quite similar to those found in Acanthamoeba profi
lin I [Archer, S. J., Vinson, V. K., Pollard, T. D., & Torchia, D. A.
(1993), Biochemistry 32, 6680-6687], suggesting that the three-dimensi
onal structure of Acanthamoeba profilin I should be analogous to that
determined here for human profilin. The structure determination of hum
an profilin has facilitated the sequence alignment of lower eukaryotic
and human profilins and provides a framework upon which the various f
unctionalities of profilin can be explored. At least one element of th
e actin-binding region of human profilin is an alpha-helix. Two mechan
isms by which phosphatidylinositol 4,5-bisphosphate can interfere with
actin-binding by human profilin are proposed.