Structural and mechanistic insights into ras association domains of phospholipase C epsilon

Ras proteins signal to a number of distinct pathways by interacting with diverse effectors. Studies of ras/effector interactions have focused on three classes, Raf kinases, ral guanylnucleotide-exchange factors, and phosphatidylinositol-3-kinases. Here we describe ras interactions with another effector, the recently identified phospholipase C epsilon (PLCepsilon). We solved structures of PLCepsilon RA domains (RA1 and RA2) by NMR and the structure of the RA2/ras complex by X-ray crystallography. Although the similarity between ubiquitin-like folds of RA1 and RA2 proves that they are homologs, only RA2 can bind ras. Some of the features of the RA2/ras interface are unique to PLCepsilon, while the ability to make contacts with both switch I and II regions of ras is shared only with phosphatidylinositol-3-kinase. Studies of PLCepsilon regulation suggest that, in a cellular context, the RA2 domain, in a mode specific to PLCepsilon, has a role in membrane targeting with further regulatory impact on PLC activity.     

西藏浪错兰格湖裸鲤的年龄与生长

2017年7月—2018年5月,于西藏自治区昂仁县浪错采集268尾兰格湖裸鲤Gymnocypris chui开展种群年龄结构和生长特征研究。结果显示:雌、雄鱼体长与体质量的关系式分别为W♀=2.03×10-2L2.822(n=134,R2=0.969)、W♂=2.52×10-2L2.738(n=105,R2=0.966)。通过观察微耳石,发现样本由1~23龄组成;采用VonBertalanffy生长方程拟合雌、雄鱼体长、体质量生长方程:Lt♀=34.239[1-e-0.136(t+0.11)]、Wt♀=434.42[1-e-0.136(t+0.11)]2.822;Lt♂=32.201[1-e-0.136(t+0.287)]、Wt♂=338.8[1-e-0.136(t+0.287)]2.738;拐点年龄分别为7.52龄和7.12龄,对应体长分别为22.12cm和20.45cm,体质量分别为126.59g和97.71g。初步研究表明,兰格湖裸鲤生长慢、体型小,种群被破坏后不易恢复,亟待开展资源评估及保护工作。