Institute of Chemistry, University of Tartu, Ravila 14a, Tartu 50411, Estonia.
Bioorg Chem. 2011 Aug;39(4):133-7. doi: 10.1016/j.bioorg.2011.04.001. Epub 2011 May 7.
Peptidomimetic analogs of the hexapeptide RRASVA, containing simultaneously two aza-β(3)-amino acid residues in different positions of this sequence, except for the phosphorylatable serine residue, were synthesized and tested as substrates for the cAMP-dependent protein kinase catalytic subunit. All these peptidomimetics were phosphorylated by the enzyme and this reaction was characterized by the K(m) and k(cat) values as well as by the second-order rate constants k(II). Affinity and reactivity of all peptidomimetics was lower than that for the parent peptide RRASVA. The effect of backbone modification was dependent upon the positions where these two aza-β(3) residues were located, although the sequence of amino acid side groups remained the same in all compounds. It was found that the influence of two backbone modifications in the substrate structure was not described additively, i.e. the effect of each structural alteration was dependent upon the position of the second modification. The results were in agreement with the concept of specificity-determining clusters in the sequence of peptide and peptidomimetic ligands, which predominantly determine the molecular recognition of these ligands by their target sites and therefore serve as major modification points for the design of activity of peptidomimetic ligands.
同时含有两个非天然的β（3）-氮基氨基酸残基的六肽 RRASVA 的肽模拟物被合成，并作为环腺苷酸依赖的蛋白激酶催化亚基的底物进行了测试。所有这些肽模拟物都能被酶磷酸化，该反应的 K(m)和 k(cat)值以及二级速率常数 k(II)都能被确定。所有肽模拟物的亲和性和反应性都低于母肽 RRASVA。这种骨架修饰的效果取决于这两个非天然β（3）残基所在的位置，尽管所有化合物的氨基酸侧链基团的序列都相同。结果发现，底物结构中两种骨架修饰的影响不能被简单地加和描述，即每个结构改变的效果取决于第二个改变的位置。这些结果与肽和肽模拟配体序列中决定特异性的决定簇的概念一致，这些决定簇主要决定这些配体与靶位的分子识别，因此是设计肽模拟配体活性的主要修饰点。
