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The trisaccharide 1-kestose, a major constituent of fructooligosaccharide, has strong prebiotic effects. We used high-performance liquid chromatography and 1H nuclear magnetic resonance spectroscopy to show that BiBftA, a β-fructosyltransferase belonging to glycoside hydrolase family 68, from Beijerinckia indica subsp. indica catalyzes transfructosylation of sucrose to produce mostly 1-kestose and levan polysaccharides. We substituted His395 and Phe473 in BiBftA with Arg and Tyr, respectively, and analyzed the reactions of the mutant enzymes with 180 g/L sucrose. The ratio of the molar concentrations of glucose and 1-kestose in the reaction mixture with wild-type BiBftA was 100:8.1, whereas that in the reaction mixture with the variant H395R/F473Y was 100:45.5, indicating that H395R/F473Y predominantly accumulated 1-kestose from sucrose. The X-ray crystal structure of H395R/F473Y suggests that its catalytic pocket is unfavorable for binding of sucrose while favorable for transfructosylation., (© The Author(s) 2023. Published by Oxford University Press on behalf of Japan Society for Bioscience, Biotechnology, and Agrochemistry.)

Jaw1/LRMP is a membrane protein that is localized to the endoplasmic reticulum and outer nuclear membrane. Previously, we revealed that Jaw1 functions to maintain nuclear shape by interacting with microtubules as a Klarsicht/ANC-1/Syne/homology (KASH) protein. The loss of several KASH proteins causes defects in the position and shape of the Golgi apparatus as well as the nucleus, but the effects of Jaw1 depletion on the Golgi apparatus were poorly understood. Here, we found that siRNA-mediated Jaw1 depletion causes Golgi fragmentation with disordered ribbon structure in the melanoma cell, accompanied by the change in the localization of the Golgi-derived microtubule network. Thus, we suggest that Jaw1 is a novel protein to maintain the Golgi ribbon structure, associated with the microtubule network., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Japanese Biochemical Society. All rights reserved.)

Jaw1/LRMP is characterized as a Type II integral membrane protein that is localized to endoplasmic reticulum, however, its physiological functions have been poorly understood. An alignment of amino acid sequence of Jaw1 with Klarsicht/ANC-1/Syne/homology (KASH) proteins, outer nuclear membrane proteins, revealed that Jaw1 has a partial homology to the KASH domain. Here, we show that the function of Jaw1 is to maintain nuclear shape in mouse melanoma cell line. The siRNA-mediated knockdown of Jaw1 caused a severe defect in nuclear shape, and the defect was rescued by ectopic expression of siRNA-resistant Jaw1. Since co-immunoprecipitation assay indicates that Jaw1 interacts with Sad-1/UNC-84 (SUN) proteins that are inner nuclear proteins and microtubules, this study suggests that Jaw1 has a role in maintaining nuclear shape via interactions with SUN proteins and microtubules.