Zhou Huaijin, Lutkenhaus Joe
Department of Microbiology, Molecular Genetics and Immunology, University of Kansas Medical Center, Kansas City, Kansas 66160-7420, USA.
J Bacteriol. 2003 Aug;185(15):4326-35. doi: 10.1128/JB.185.15.4326-4335.2003.
MinD binds to phospholipid vesicles in the presence of ATP and is released by MinE, which stimulates the MinD ATPase. Membrane binding requires a short conserved C-terminal region, which has the potential to form an amphipathic helix. This finding has led to a model in which the binding of ATP regulates the formation or accessibility of this helix, which then embeds in the membrane bilayer. To test this model, we replaced each of the four hydrophobic residues within this potential helix with tryptophan or a charged residue. Introduction of a negatively charged amino acid decreased membrane binding of MinD and its ability to activate MinC. In contrast, mutants with tryptophan substitutions retained the ability to bind to the membrane and activate MinC. Fluorescence emission spectroscopy analysis of the tryptophan mutants F263W, L264W, and L267W confirmed that these tryptophan residues did insert into the hydrophobic interior of the bilayer. We conclude that membrane binding by MinD involves penetration of the hydrophobic residues within the C-terminal amphipathic helix into the hydrophobic interior of the bilayer.
在ATP存在的情况下，MinD与磷脂囊泡结合，并被刺激MinD ATP酶的MinE释放。膜结合需要一个短的保守C末端区域，该区域有可能形成两亲性螺旋。这一发现导致了一个模型，其中ATP的结合调节该螺旋的形成或可及性，然后该螺旋嵌入膜双层中。为了测试这个模型，我们用色氨酸或带电荷的残基替换了这个潜在螺旋中的四个疏水残基中的每一个。引入带负电荷的氨基酸降低了MinD的膜结合及其激活MinC的能力。相反，色氨酸替代突变体保留了与膜结合并激活MinC的能力。对色氨酸突变体F263W、L264W和L267W的荧光发射光谱分析证实，这些色氨酸残基确实插入了双层的疏水内部。我们得出结论，MinD的膜结合涉及C末端两亲性螺旋内的疏水残基渗透到双层的疏水内部。
