Human RNase 1 can extensively oligomerize through 3D domain swapping thanks to the crucial contribution of its C-terminus.

Human ribonuclease (RNase) 1 and bovine RNase A are the proto-types of the secretory "pancreatic-type" (pt)-RNase super-family. RNase A can oligomerize through the 3D domain swapping (DS) mechanism upon acetic acid (HAc) lyophilisation, producing enzymatically active oligomeric conformers by swapping both N- and C-termini. Also some RNase 1 mutants were found to self-associate through 3D-DS, however forming only N-swapped dimers. Notably, enzymatically active dimers and larger oligomers of wt-RNase 1 were collected here, in higher amount than RNase A, from HAc lyophilisation. In particular, RNase 1 self-associates through the 3D-DS of its N-terminus and, at a higher extent, of the C-terminus. Since RNase 1 is four-residues longer than RNase A, we further analyzed its oligomerization tendency in a mutant lacking the last four residues. The C-terminus role has been investigated also in amphibian onconase (ONC®), a pt-RNase that can form only a N-swapped dimer, since its C-terminus, that is three-residues longer than RNase A, is locked by a disulfide bond. While ONC mutants designed to unlock or cut this constraint were almost unable to dimerize, the RNase 1 mutant self-associated at a higher extent than the wt, suggesting a specific role of the C-terminus in the oligomerization of different RNases. Overall, RNase 1 reaches here the highest ability, among pt-RNases, to extensively self-associate through 3D-DS, paving the way for new investigations on the structural and biological properties of its oligomers.

Microbiological profile of raw refrigerated and processed bovine milk at dairy industries from Vale do Taquari, Rio Grande do Sul, Brazil

Milk is an essential food, widely consumed by the population. Brazil is one of the world's largest producers of milk. Milk quality is influenced by several factors in all its stages of production. The aim of this study was to determine the microbiological profile of refrigerated and processed raw bovine milk from industries in Vale do Taquari, state of Rio Grande do Sul, Brazil, using metagenomic analysis. A total of six samples were collected, one of refrigerated raw milk from the tanker truck, one of pasteurized milk and one of milk sterilized by the ultra-high temperature (UHT) process, in each of the industries. The identification of the milk microbiota was performed by sequencing the 16S rRNA gene. The results show that refrigerated raw milk has a greater number of microorganisms, followed by pasteurized milk and sterilized milk, successively. Processed milk showed the presence of beneficial microorganisms such as Streptococcus thermophilus and Streptococcus macedonicus. Nevertheless, even UHT milk showed the presence of microorganisms considered harmful, such as the Bacillus cereus group, Aeromonas dhakensis, Enterobacter bacterium and Acinetobacter haemolyticus. Metagenomics is a valuable tool for the thorough evaluation of the milk microbiota in order to implement the processing stages in industries.