th  - 1987 - 51st ENC Conference

WK16
MULTINUCLEAR SOLID STATE NMR STUDIES OF INTERNAL MOLECULAR DYNAMICS IN
FIBROUS AND CRYSTALLINE PROTEINS
Y. Hiyama*, J. W. Hack +, S. W. Sparks** and D. A. Torchla,
Natlonal Institute of Dental Research, Natlonal Institutes of Health
Bethesda, Maryland 20892
Collagen*: Intact rabbit Achilles tendon collagen containing
4-fluorophenylalanine (provided by Dr. J. T. Gerlg) has been studied by
19F NMR at 470 MHz. Analysls of the 19F CSA powder patterns obtained at
-37°C show that motion of all amino acid sldechains is restricted to small
angle rolling or rare 180 ° fllps of the phenyl ring. In contrast, above
-4°C, the powder pattern indicates considerable heterogenlety in the
dynamics of the sidechaln, a result that will be discussed with reference
to collagen fiber structure.
Keratin+: Assembled intermediate filaments of mouse epidermal
keratin, labeled with 13C and 2H (provided by Dr. Peter Steinert) have
been studied at several field strengths. Analysls of measurements of
Tl'S, llne widths and NOE values of filaments labeled with [I-13C] and
[2-13C] glyclne show that the protein backbone, in the non-helical N- and
C-terminal domains, is Isotropically mobile on the nanosecond timescale.
Deuterium llneshapes of leucyl residues, located in the interior helical
domain of the protein show that motions of these sidechains are
anisotropic. We will report on the spatial extent and timescale of these
sidechalr motions based on our analysis of the 2H lineshape and relaxa-
tlon data.
Staphylococcal Nuclease~'#: Using genetically engineered E. Coli
(provided by Dr. J. Gerlt) we have prepared crystals of S. Nuclease
containing residue specific NNR spin labels. Deuterium lineshapes show
that except for methyl rotation, molecular motion is highly restricted at
temperatures below -35°C. In contrast, at 20°C, at least one half of each
of the Pro, Met, Phe and Tyr residues execute large amplitude sidechain
motions. The detailed nature and timescale of these motions will be dis-
cussed and, where possible, related to the crystal structure. These are
the first extensive measurements of internal motions in a protein crystal
and clearly show that even in crystals proteins are dynamic structures.