分类: 生物学 >> 生物物理学 提交时间: 2016-05-11
摘要: Electron transfer (ET) is widely used for driving the processes that underlie the chemistry of life. However, our abilities to probe electron transfer mechanisms in proteins and design redox enzymes are limited, due to :the lack of methods to site-specifically insert electron acceptors into proteins in vivo. Here we describe the synthesis and genetic incorporation of 4-fluoro-3-nitrophenylalanine (FNO(2)Phe), which has similar reduction potentials to NAD(P)H and ferredoxin, the most important biological reductants. Through the genetic incorporation of FNO2Phe into green fluorescent:protein (GFP) and femtosecond transient absorption measurement, we show that photoinduced electron transfer (PET) from the GFP chromophore to FNO2Phe occurs very fast (within 11 ps), which is comparable to that of the first electron transfer step in photosystem I, from P700* to A(0). This genetically encoded, low-reduction potential unnatural amino acid (UAA) can significantly in-Trove our ability to investigate electron transfer mechanisms in complex reductases and facilitate the design of miniature proteins that mimic their functions.
分类: 生物学 >> 生物物理学 >> 生物物理、生物化学与分子生物学 提交时间: 2016-05-11
摘要: Cerebral cavernous malformation 2 (CCM2) functions as an adaptor protein implicated in various biological processes. By interacting with the mitogen-activated protein kinase MEKK3, CCM2 either mediates the activation of MEKK3 signaling in response to osmotic stress or negatively regulates MEKK3 signaling, which is important for normal cardiovascular development. However, the molecular basis governing CCM2-MEKK3 interaction is largely unknown. Here we report the crystal structure of the CCM2 C-terminal part (CCM2ct) containing both the five-helix domain (CCM2ct(s)) and the following C-terminal tail. The end of the C-terminal tail forms an isolated helix, which interacts intramolecularly with CCM2ct(s). By biochemical studies we identified the N-terminal amphiphilic helix of MEKK3 (MEKK3-n(helix)) as the essential structural element for CCM2ct binding. We further determined the crystal structure of CCM2ct(s)-MEKK3-n(helix) complex, in which MEKK3-n(helix) binds to the same site of CCM2ct(s) for CCM2ct intramolecular interaction. These findings build a structural framework for understanding CCM2ct-MEKK3 molecular recognition.