Sorghum procyanidins (SPC) tetramers were reported to have inhibitory effects on the adhesion of Streptococcus mutans (S. mutans), which is one of the primary pathogenic bacteria that cause caries. To make clear the mechanism underlying the inhibitory effects of SPC tetramers on the adhesion of S. mutans, it is important to understand the interaction between SPC tetramers and the catalytic region of glucosyltransferases-I (GTF-I/CAT) from S. mutans. In this study, fluorescence quenching, UV–visible (UV–Vis) absorption and circular dichroism (CD) spectroscopies were applied to investigate the interaction between SPC tetramers and the GTF-I/CAT from S. mutans UA159. The fluorescence quenching results demonstrated that SPC tetramers combined with GTF-I/CAT protein on one binding site, and the fluorescence intensity of GTF-I/CAT protein was decreased regularly by static quenching with increasing concentrations of SPC tetramers. The UV–Vis absorption spectra of GTF-I/CAT protein were also changed with a red shift owing to the impact of SPC tetramers. In addition, the proportions of α-helix, β-sheet and random coil in the secondary structure of GTF-I/CAT protein were obviously altered by SPC tetramers. In conclusion, SPC tetramers have a strong affinity for GTF-I/CAT protein by altering its conformation and micro-environment. Our results suggest that SPC tetramers interact with GTF-I/CAT to interfere with the adhesion of S. mutans, which may facilitate the better application of SPC tetramers in the prevention of dental caries.

据报道，高粱原花青素（SPC）四聚体对变形链球菌（变形链球菌）的粘附具有抑制作用，变形链球菌是引起龋齿的主要致病细菌之一。为弄清SPC四聚体对变形链球菌粘附的抑制作用的潜在机制，重要的是了解SPC四聚体与变形链球菌葡糖基转移酶-I（GTF-I / CAT）催化区域之间的相互作用。在这项研究中，荧光猝灭，紫外可见（UV-Vis）吸收和圆二色性（CD）光谱用于研究SPC四聚体与变形链球菌GTF-I / CAT之间的相互作用。UA159。荧光猝灭结果表明，SPC四聚体与GTF-I / CAT蛋白结合在一个结合位点上，随着SPC四聚体浓度的增加，通过静态猝灭使GTF-I / CAT蛋白的荧光强度有规律地降低。由于SPC四聚体的影响，GTF-I / CAT蛋白的UV-Vis吸收光谱也发生了红移。此外，SPC四聚体明显改变了GTF-I / CAT蛋白二级结构中α-螺旋，β-折叠和无规卷曲的比例。总之，SPC四聚体通过改变其构象和微环境，对GTF-I / CAT蛋白具有很强的亲和力。我们的结果表明，SPC四聚体与GTF-I / CAT相互作用以干扰变形链球菌的黏附，这可能有助于更好地应用SPC四聚体预防龋齿。