Protein integration into biological membranes is a vital cellular event for all organisms. We previously reported an integration factor in the inner membrane of Escherichia coli, named MPIase (membrane protein integrase). Here we show that in contrast to previously identified integration factors that are proteins, MPIase is a glycolipid composed of diacylglycerol and a glycan chain of three acetylated aminosugars linked through pyrophosphate. Hydrolytic removal of the lipid moiety gives a soluble product with higher integration activity than that of the original MPIase. This soluble form of MPIase directly interacts with a newborn membrane protein, maintaining its integration-competent structure and allowing its post-translational integration. MPIase actively drives protein integration following chaperoning membrane proteins. We further demonstrate with anti-MPIase antibodies that MPIase is likely involved in integration in vivo. Collectively, our results suggest that MPIase, essential for membrane protein integration, is to our knowledge the first glycolipid with an enzyme-like activity.

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Rapid analysis of 90Sr in bone and tooth samples of cattle was conducted by inductively coupled plasma mass spectrometry (ICP-MS) coupled with mass-shift and solid-phase extraction techniques. The mass-shift technique...

This paper describes the result of transient experiments using low enriched uranium silicide plate-type fuel for research reactors. The pulse irradiation was carried out at Nuclear Safety Research Reactor (NSRR) in Japan Atomic Energy Research Institute. The results obtained were: (1) At fuel plate temperature of below 4oo•c, a good dimensional stability of the tested fuel was kept. No fuel failure occurred. (2) At a plate temperature of about 54o•c, a local crack was initiated on the AI-3%Mg alloy cladding. Once the cladding temperature exceeded the melting point of 640'C, the fuel plate was degraded much by increased bowing and cracking of the denuded fuel meat occurred after relocation of molten AI cladding. Despite of these degradation, neither fragmentation of the fuel plate nor mechanical energy generation occurred up to the cladding temperature of 971 'C. (3) At the temperatures of around 925'C, the reaction of silicide particles with molten At in the matrix and that of cladding occurred, forming AI riched U (AI, Si) compounds and Si riched (U, Si) compounds at the outermost surface of the silicide particles.