Dalgleish D G, Peacocke A R
Biochem J. 1971 Nov;125(1):155-8. doi: 10.1042/bj1250155.
The circular-dichroism (CD) spectra of beta-lactamases I and II from Bacillus cereus 569/H are reported, along with that of the beta-lactamase II free from carbohydrate. The results show that carbohydrate makes an appreciable contribution to the optical activity of beta-lactamase II in the far-ultraviolet, and that removal of carbohydrate greatly affects the optical activity of several aromatic side chains of the protein moiety. Both tyrosyl and tryptophanyl residues are affected, showing that some of these residues must be near to the surface of the protein moiety, close to the site of attachment of the carbohydrate. Although the far-ultraviolet CD spectrum of beta-lactamase II resembles that of a protein containing some beta-structure, it can be shown that this is a consequence of the optical activity of carbohydrate in this region of the spectrum, and that the protein is likely to contain alpha-helix rather than beta-pleated sheet structure. The overall structures of the protein components of beta-lactamases I and II are similar, but not identical, as shown by the dissimilarity of the CD spectra when calculated on a mean residue basis.
报道了蜡样芽孢杆菌569/H中β-内酰胺酶I和II的圆二色性（CD）光谱，以及不含碳水化合物的β-内酰胺酶II的光谱。结果表明，碳水化合物对β-内酰胺酶II在远紫外区的光学活性有显著贡献，去除碳水化合物会极大地影响蛋白质部分几个芳香族侧链的光学活性。酪氨酸残基和色氨酸残基均受影响，表明这些残基中的一些必定靠近蛋白质部分的表面，靠近碳水化合物的附着位点。尽管β-内酰胺酶II的远紫外CD光谱类似于含有一些β-结构的蛋白质的光谱，但可以证明这是该光谱区域中碳水化合物光学活性的结果，并且该蛋白质可能含有α-螺旋而非β-折叠片层结构。如以平均残基为基础计算时CD光谱的差异所示，β-内酰胺酶I和II的蛋白质组分的整体结构相似但不相同。
