FGD2, a member of FGD family, contains a Dbl homology domain (DH) and two pleckstrin homology domains segregated by a FYVE domain. The DH domain has been deduced to be responsible for guanine nucleotide exchange of CDC42 to activate downstream factors. Our aim was to build a prokaryotic expression system for the DH domain and to examine its guanine nucleotide exchange activity toward CDC42 in vitro. A recombinant vector, which was successfully constructed based on pGEX-6P-1, was employed to express the DH domain of human FGD2 (FGD2-DH) in E. coli BL21 (DE3). Purified FGD2-DH behaved as a homogeneous monomer with an estimated molecular weight that corresponded to the theoretical molecular weight and was predicted to be an α-helix protein by circular dichroism spectroscopy. FGD2-DH displayed weak guanine nucleotide exchange activity in vitro and very weak interactions with CDC42 following glutaraldehyde cross-linking.

FGD2的成员FGD2包含一个Dbl同源域（DH）和两个由FYVE域分隔的pleckstrin同源域。推测DH结构域负责CDC42的鸟嘌呤核苷酸交换以激活下游因子。我们的目的是建立一个DH域的原核表达系统，并在体外研究其对CDC42的鸟嘌呤核苷酸交换活性。基于pGEX-6P-1成功构建的重组载体用于在大肠杆菌中表达人FGD2的DH结构域（FGD2-DH）BL21（DE3）。纯化的FGD2-DH表现为均质单体，其估计分子量与理论分子量相对应，并且通过圆二色谱法预测为α-螺旋蛋白。FGD2-DH体外显示弱的鸟嘌呤核苷酸交换活性，戊二醛交联后与CDC42的相互作用非常弱。