Kettunen R, Tyystjärvi E, Aro E M
Department of Biology, University of Turku, Finland. reeket/utu.fi
Plant Physiol. 1996 Aug;111(4):1183-90. doi: 10.1104/pp.111.4.1183.
Photoinhibition-induced degradation of the D1 protein of the photosystem II reaction center was studied in intact pumpkin (Cucurbita pepo L.) leaves. Photoinhibition was observed to cause the cleavage of the D1 protein at two distinct sites. The main cleavage generated an 18-kD N-terminal and a 20-kD C-terminal degradation fragment of the D1 protein. this cleavage site was mapped to be located clearly N terminally of the DE loop. The other, less-frequent cleavage occurred at the DE loop and produced the well-documented 23-kD, N-terminal D1 degradation product. Furthermore, the 23-kD, N-terminal D1 fragment appears to be phosphorylated and can be detected only under severe photoinhibition in vivo. Comparison of the D1 degradation pattern after in vivo photoinhibition to that after in vitro acceptor-side and donor-side photoinhibition, performed with isolated photosystem II core particles, gives indirect evidence in support of donor-side photoinhibition in intact leaves.
在完整的南瓜（西葫芦）叶片中研究了光抑制诱导的光系统II反应中心D1蛋白的降解。观察到光抑制导致D1蛋白在两个不同位点发生裂解。主要裂解产生了D1蛋白的一个18-kD N端和一个20-kD C端降解片段。该裂解位点被定位在DE环的N端明显位置。另一个不太常见的裂解发生在DE环，产生了有充分记录的23-kD N端D1降解产物。此外，23-kD N端D1片段似乎被磷酸化，并且仅在体内严重光抑制条件下才能检测到。将体内光抑制后的D1降解模式与用分离的光系统II核心颗粒进行的体外受体侧和供体侧光抑制后的降解模式进行比较，为完整叶片中供体侧光抑制提供了间接证据支持。
