Seidler A, Rutherford A W, Michel H
CNRS URA 1290, Département de Biologie Cellulaire et Moléculaire, CEA Saclay, Gif-sur-Yvette, France.
Plant Mol Biol. 1996 Apr;31(1):183-8. doi: 10.1007/BF00020619.
The role of the N-terminus of the extrinsic 33 kDa protein of Photosystem II has been investigated by means of site-directed mutagenesis and cross-linking. Replacement of Asp-9 resulted in a dramatic increase in proteolytic sensitivity leading to the degradation of the protein forming a 31 kDa fragment with an undefined N-terminus. This fragment was unable to restore oxygen evolution. However, the variants of the 33 kDa protein which remained intact could reconstitute oxygen evolution as effectively as the wild-type protein. Cross-linking experiments with a water-soluble carbodiimide revealed that mutagenesis of residue D9 led to the disruption of an intramolecular salt bridge. Therefore we suggest that the N-terminus of the 33 kDa protein is necessary for maintaining the binding ability of the protein to Photosystem II but might not be involved in binding itself.
通过定点诱变和交联的方法研究了光系统II外在33 kDa蛋白N端的作用。将天冬氨酸-9替换后，蛋白对蛋白酶的敏感性显著增加，导致该蛋白降解，形成一个N端未明确的31 kDa片段。这个片段无法恢复氧气释放。然而，保持完整的33 kDa蛋白变体能够像野生型蛋白一样有效地重建氧气释放。用水溶性碳二亚胺进行的交联实验表明，残基D9的诱变导致分子内盐桥的破坏。因此，我们认为33 kDa蛋白的N端对于维持该蛋白与光系统II的结合能力是必要的，但可能不参与其自身的结合。
