Comparison of alpha-lactalbumin and lysozyme using vibrational circular dichroism. Evidence for a difference in crystal and solution structures.
The conformation of the milk protein alpha-lactalbumin has been studied using vibrational circular dichroism (VCD) and compared to parallel studies on lysozyme. These proteins have been shown by Acharya et al. [(1989) J. Mol. Biol. 208, 99-127] to have very similar three-dimensional crystal structures. However, their VCD spectra in D2O solution are quite different. The VCD of lysozyme in D2O more resembles that of alpha-lactalbumin in 33% propanol/D2O, under which conditions alpha-lactalbumin has conformationally transformed to a structure with increased helical fraction. These results can be seen to be consistent with UVCD and resolution-enhanced FTIR spectra of alpha-lactalbumin and lysozyme in both D2O and H2O environments. The solvent sensitivity of the alpha-lactalbumin spectra and hence of its conformation contrasted with the lack of such sensitivity for lysozyme suggest that the alpha-lactalbumin crystal structure represents a conformation different from that which is dominant in aqueous solution.
Department of Chemistry, University of Illinois, Chicago 60680.
M
M
Urbanova
R K
RK
Dukor
P
P
Pancoska
V P
VP
Gupta
T A
TA
Keiderling
D000818:Animals; D002417:Cattle; D002645:Chickens; D002942:Circular Dichroism; D003460:Crystallization; D005260:Female; D007768:Lactalbumin / Q000737:chemistry*; D009113:Muramidase / Q000737:chemistry*; D011487:Protein Conformation; D013055:Spectrophotometry, Infrared; D014732:Vibration
D007768:Lactalbumin; D009113:Muramidase