Pukala Tara L, Brinkworth Craig S, Carver John A, Bowie John H
Department of Chemistry, The University of Adelaide, Adelaide, South Australia 5005, Australia.
Biochemistry. 2004 Feb 3;43(4):937-44. doi: 10.1021/bi035760b.
Caerin 1.1 is a potent broad-spectrum antibacterial peptide isolated from a number of Australian frogs of the Litoria genus. In membrane-like media, this peptide adopts two alpha-helices, separated by a flexible hinge region bounded by Pro15 and Pro19. Previous studies have suggested that the hinge region is important for effective orientation of the two helices within the bacterial cell membrane, resulting in lysis via the carpet mechanism. To evaluate the importance of the two Pro residues, they were replaced with either Ala or Gly. The antibacterial activity of these two peptides was tested, and their three-dimensional structures were determined using two-dimensional NMR spectroscopy and restrained molecular dynamics calculations. The resulting structures indicate that the central hinge angle decreases significantly upon replacement of the Pro residues with Gly and to a further extent with Ala. This trend was mirrored by a corresponding decrease in antibiotic activity, further exemplifying the necessity of the hinge in caerin 1.1 and related peptides. In a broader context, the use of Pro, Gly, and Ala variants of caerin 1.1 has enabled the relationship between conformational flexibility and activity to be directly investigated in a systematic manner.
Caerin 1.1是一种从多种澳大利亚林蛙属青蛙中分离出的强效广谱抗菌肽。在类膜介质中，这种肽会形成两个α螺旋，由一个以Pro15和Pro19为界的柔性铰链区隔开。先前的研究表明，铰链区对于两个螺旋在细菌细胞膜内的有效定向很重要，通过毯式机制导致细胞裂解。为了评估这两个脯氨酸残基的重要性，将它们替换为丙氨酸或甘氨酸。测试了这两种肽的抗菌活性，并使用二维核磁共振光谱和受限分子动力学计算确定了它们的三维结构。所得结构表明，用甘氨酸取代脯氨酸残基后，中心铰链角显著减小，用丙氨酸取代时减小程度更大。这种趋势与抗生素活性的相应降低相对应，进一步证明了Caerin 1.1及相关肽中铰链的必要性。在更广泛的背景下，使用Caerin 1.1的脯氨酸、甘氨酸和丙氨酸变体能够以系统的方式直接研究构象灵活性与活性之间的关系。
