Sanford D G, Kanagy C, Sudmeier J L, Furie B C, Furie B, Bachovchin W W
Department of Biochemistry, Tufts University School of Medicine, Boston, Massachusetts 02111.
Biochemistry. 1991 Oct 15;30(41):9835-41. doi: 10.1021/bi00105a004.
The propeptides of the vitamin K dependent blood clotting and regulatory proteins contain a gamma-carboxylation recognition site that directs precursor forms of these proteins for posttranslational gamma-carboxylation. Peptides corresponding to the propeptide of prothrombin were synthesized and examined by circular dichroism (CD) and nuclear magnetic resonance spectroscopy (NMR). CD spectra indicate that these peptides have little or no secondary structure in aqueous solutions but that the addition of trifluoroethanol induces or stabilizes a structure containing alpha-helical character. The maximum helical content occurs at 35-40% trifluoroethanol. This trifluoroethanol-stabilized structure was solved by two-dimensional NMR spectroscopy. The NMR results demonstrate that residues -13 to -3 form an amphipathic alpha-helix. NMR spectra indicate that a similar structure is present at 5 degrees C, in the absence of trifluoroethanol. Of the residues previously implicated in defining the gamma-carboxylation recognition site, four residues (-18, -17, -16, and -15) are adjacent to the helical region and one residue (-10) is located within the helix. The potential role of the amphipathic alpha-helix in the gamma-carboxylation recognition site is discussed.
维生素K依赖性凝血蛋白和调节蛋白的前肽含有一个γ-羧化识别位点，该位点指导这些蛋白的前体形式进行翻译后γ-羧化。合成了与凝血酶原前肽相对应的肽，并通过圆二色性（CD）和核磁共振光谱（NMR）进行检测。CD光谱表明，这些肽在水溶液中几乎没有二级结构，但加入三氟乙醇会诱导或稳定一种具有α-螺旋特征的结构。最大螺旋含量出现在35%-40%的三氟乙醇中。通过二维核磁共振光谱解析了这种三氟乙醇稳定的结构。NMR结果表明，残基-13至-3形成一个两亲性α-螺旋。NMR光谱表明，在5摄氏度且不存在三氟乙醇的情况下也存在类似结构。在先前涉及定义γ-羧化识别位点的残基中，有四个残基（-18、-17、-16和-15）与螺旋区域相邻，一个残基（-10）位于螺旋内。讨论了两亲性α-螺旋在γ-羧化识别位点中的潜在作用。
