Molecular Interactions Involved In Gal Repression

我们利用分析超速离心机研究了参与Gal抑制的相互作用。抑制环显然涉及GalR与DNA上的半乳糖操纵子位点的结合，但为了发生抑制，已经发现HU的存在是必要的。我们首先分别研究了HU和GalR的自联想性质，建立了自联想的模式和强度。随后研究了GalR与含有两个半乳糖操纵子之一的寡核苷酸(29个碱基对的寡核苷酸)的结合。最后加入HU，利用先前建立的结合模式和它们的结合强度，我们推断一对HU单体与GalR二聚体结合到寡核苷酸的络合物上。确定了缔合强度，其结果与能量转移荧光和偏振各向异性测量的结果一致。

We studied the interaction involved in Gal repression using the analytical ultracentrifuge. The repression loop apparently involves binding of GalR to the galactose operator sites on the DNA but for suppression to occur the presence of HU has been found to be necessary. We studied first the self association properties of HU and GalR separately to establish the patterns and strengths of the self-associations. This was followed by the study of the binding of GalR to the oligonucleotide containing one of the two galactose operators (a 29 base-pair oligonucleotide). Finally HU was added and using the previously established association patterns and their association strengths we deduced that a pair of HU monomers binds to the complex of the oligonucleotide with a GalR dimer. The association strength was also established and the results were consistent with those obtained by energy transfer fluorescence and polarization anisotropy measurements.