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Summary The ubiquitin-proteasome system is a vital proteolytic pathway required for cell homeostasis. However, the turnover mechanism of the proteasome subunit itself is still not understood. Here, we show that the 20S proteasome subunit PSMA7 is subjected to ubiquitination and proteasomal degradation, which was suppressed by PSMA7 phosphorylation at Y106 mediated by the nonreceptor tyrosine kinases c-Abl/Arg. BRCA1 specifically functions as an E3 ubiquitin ligase of PSMA7 ubiquitination. c-Abl/Arg regulates cellular proteasome abundance by controlling the PSMA7 subunit supply. Downregulated PSMA7 level results in decreased proteasome abundance in c-Abl/Arg RNAi-knockdown or c-abl / arg -deficient cells, which demonstrated an increased sensitivity to proteasome inhibition. In response to oxidative stress, the c-Abl-mediated upregulation of proteasome level compensates for the proteasomal activity impairment induced by reactive oxygen species. Abl-kinases-regulated biogenesis and homeostasis of proteasome complexes may be important for understanding related diseases and pathological states. [ABSTRACT FROM AUTHOR]

Abstract: This paper briefly reviews contemporary protein crystallography and focuses on six receptor proteins of membrane-intrinsic ATP binding cassette (ABC) transporters. Three of these receptors are specific for carbohydrates and three for amino acids. The receptor GacH of the transporter GacFGH from Streptomyces glaucescens is specific for acarbose and its homologs, and MalE of Salmonella typhimurium is specific for maltose but also forms a complex with acarbose, and the third receptor is the highly specific d-galactose receptor AcbH of the transporter AcbFGH from Actinoplanes sp. Concerning the receptors for amino acids, ArtJ belongs to the ArtJ-(MP)2 transporter of Geobacillus stearotermophilus and recognizes and binds to positively charged arginine, lysine, and histidine with different sizes of side chains, contrasting the receptors Ngo0372 and Ngo2014 from Neisseria gonorrhaeae that are highly specific for cystine and cysteine, respectively. The differences in the rather unspecific receptors GacH, MalE and ArtJ are compared with the highly specific receptors AcbH, Ngo0372 and Ngo2014. [Copyright &y& Elsevier]

Abstract: Acid-mediated ring-transformations of 5-alkylidene-2,5-dihydropyrrol-2-ones, available by cyclization of 1,3-diketone dianions with bis(imidoyl) dichlorides of oxalic acid, resulted in formation of functionalized pyran-4-ones, such as 5,6-dihydrobenzo[h]chromones and 5,6,7,8-tetrahydrochromones. [Copyright &y& Elsevier]