A 1H NMR spectroscopic comparison of gamma S- and gamma B-crystallins.
Two-dimensional 1H NMR spectroscopic studies are presented on bovine gamma S- and gamma B-crystallin. In gamma S-crystallin, the four N-terminal residues have great flexibility compared with the rest of the molecule and assume a random coil conformation. NMR spectroscopy and electrospray mass spectrometry show that the N-terminal residue is acetylated. Thus, gamma S-crystallin is similar to the acidic beta-crystallins in having a flexible N-terminal extension and an N-terminus that is blocked with an acetyl group but no C-terminal extension. In addition to the short N-terminal extension in gamma S-crystallin, other unassigned resonances are also observed in the NMR spectra. In gamma B-crystallin, however, cross-peaks in the NH to alpha-CH region of the spectrum are essentially restricted to the last three residues of the C-terminal domain. The NMR data imply that gamma S-crystallin has a more flexible structure than gamma B-crystallin. Sedimentation equilibrium studies on gamma S-crystallin are consistent with this proposal. Resonances from the N-terminal extension of gamma S-crystallin are not affected by the presence of alpha-crystallin implying that this region is not involved in interactions between the two molecules. It is concluded that gamma S-crystallin shares structural properties which are intermediate between the beta- and gamma-crystallins.
Australian Cataract Research Foundation, University of Wollongong, NSW.
P G
PG
Cooper
J A
JA
Carver
J A
JA
Aquilina
G B
GB
Ralston
R J
RJ
Truscott
D000818:Animals; D002417:Cattle; D003459:Crystallins / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008970:Molecular Weight; D017434:Protein Structure, Tertiary
D003459:Crystallins