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YsxC is a small GTPase of Bacillus subtilis with essential but still unknown function, although recent works have suggested that it might be involved in ribosome biogenesis. Here, purified YsxC overexpressed in Escherichia coil was found to be partly associated with high-molecular-weight material, most likely rRNA, and thus eluted from gel filtration as a large complex. In addition, purification of ribosomes from an E. coli strain overexpressing YsxC allowed the copurification of the YsxC protein. Purified YsxC was shown to bind preferentially to the 50S subunit of B. subtilis ribosomes; this interaction was modulated by nucleotides and was stronger in the presence of a nonhydrolyzable GTP analogue than with GTP. Far-Western blotting analysis performed with [His.sub.6]-YsxC and ribosomal proteins separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that YsxC interacted with at least four ribosomal proteins from the 50S subunit. Two of these putative protein partners were identified by mass spectrometry as LI and L3, while the third reactive band in the one-dimensional gel contained L6 and L10. The fourth band that reacted with YsxC contained a mixture of three proteins, L7/L12, L23, and L27, suggesting that at least one of them binds to YsxC. Coimmobilization assays confirmed that L1, L6, and L7/L12 interact with YsxC. Together, these results suggest that YsxC plays a role in ribosome assembly.

GTPases have been demonstrated to be necessary for the proper assembly of the ribosome in bacteria and eukaryotes. Here, we show that the essential GTPases YphC and YsxC are required for large ribosomal subunit biogenesis in Bacillus subtilis. Sucrose density gradient centrifugation of large ribosomal subunits isolated from YphC-depleted cells and YsxC-depleted cells indicates that they are similar to the 45S intermediate previously identified in RbgA-depleted cells. The sedimentation of the large-subunit intermediate isolated from YphC-depleted cells was identical to the intermediate found in RbgA-depleted cells, while the intermediate isolated from YsxC-depleted cells sedimented slightly slower than 45S, suggesting that it is a novel intermediate. Analysis of the protein composition of the large-subunit intermediates isolated from either YphC-depleted cells or YsxC-depleted cells indicated that L16 and L36 are missing. Purified YphC and YsxC are able to interact with the ribosome in vitro, supporting a direct role for these two proteins in the assembly of the 50S subunit. Our results indicate that, as has been demonstrated for Saccharomyces cerevisiae ribosome biogenesis, bacterial 50S ribosome assembly requires the function of multiple essential GTPases.

A study was done on the relationship of gastric and pancreatic enzyme activities on some gut regulatory peptides during postnatal development and weaning in calves. It was shown that the values for enzyme activities increased with age for carboxypeptidases A and B, ribonuclease, alpha amylase, chymotrypsin and elastase and decreased with chymosin, colipase and lysozyme. It was further shown that enzyme regulation is modified by colostrum and milk intake as well as by weaning.

SREC-II (scavenger receptor expressed by endothelial cells II) is a membrane protein encoded by the SCARF2 gene, with high homology to class F scavenger receptor SR-F1, but no known scavenging function. We produced the extracellular domain of SREC-II in a recombinant form and investigated its capacity to interact with common scavenger receptor ligands, including acetylated low-density lipoprotein (AcLDL) and maleylated or acetylated BSA (MalBSA or AcBSA). Whereas no binding was observed for AcLDL, SREC-II ectodomain interacted strongly with MalBSA and bound with high affinity to AcBSA, a property shared with the SR-F1 ectodomain. SREC-II ectodomain also interacted with two SR-F1-specific ligands, complement C1q and calreticulin, with affinities in the 100 nm range. We proceeded to generate a stable CHO cell line overexpressing full-length SREC-II; binding of MalBSA to these cells was significantly increased compared with nontransfected CHO cells. In contrast, no increase in binding could be detected for C1q and calreticulin. We show for the first time that SREC-II has the capacity to interact with the common scavenger receptor ligand MalBSA. In addition, our data highlight similarities and differences in the ligand binding properties of SREC-II in soluble form and at the cell surface, and show that endogenous protein ligands of the ectodomain of SREC-II, such as C1q and calreticulin, are shared with the corresponding domain of SR-F1., (© 2021 The Authors. FEBS Open Bio published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.)