Bacterial microcompartments (BMCs) are prokaryotic organelles. Their bounding membrane is a selectively permeable protein shell, encapsulating enzymes of specialized metabolic pathways. While the function of a BMC is dictated by the encapsulated enzymes which vary with the type of the BMC, the shell is formed by conserved protein building blocks. The genes necessary to form a BMC are typically organized in a locus; they encode the shell proteins, encapsulated enzymes as well as ancillary proteins that integrate the BMC function into the cell's metabolism. Among these are transcriptional regulators which usually found at the beginning or end of a locus, and transmembrane proteins that presumably function to conduct the BMC substrate into the cell. Here, we describe the types of transcriptional regulators and permeases found in association with BMC loci, using a recently collected data set of more than 7000 BMC loci distributed over 45 bacterial phyla, including newly discovered BMC loci. We summarize the known BMC regulation mechanisms, and highlight how much remains to be uncovered. We also show how analysis of these ancillary proteins can inform hypotheses about BMC function; by examining the ligand-binding domain of the regulator and the transporter, we propose that nucleotides are the likely substrate for an enigmatic uncharacterized BMC of unknown function.
Depicted as playing cards belonging to the same suit, the paralogous MLL3 and MLL4 lysine methyltransferase (KMT) complexes share a common set of core and auxiliary subunits as well as similar histone methylase functions. On each card, largely divergent processes are described on opposing sides – highlighting the potential capacity of these KMT complexes to participate in both tumor-supportive and tumor-suppressive mechanisms. To understand how MLL3 and MLL4 can regulate such diverse and sometimes contrasting processes, read more in this review article by Wang and colleagues (pp. 1041–1054). Cover artwork created by Marvin Aberin with Biorender.com.
Clues to the function of bacterial microcompartments from ancillary genes
Henning Kirst, Cheryl A. Kerfeld; Clues to the function of bacterial microcompartments from ancillary genes. Biochem Soc Trans 30 June 2021; 49 (3): 1085–1098. doi: https://doi.org/10.1042/BST20200632
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