RESUMO
In human nutrition, bovine milk is an essential source of bioavailable vitamin B12 and B12-binding proteins, including transcobalamin. In this study, we estimated genetic parameters for milk content of vitamin B12 and transcobalamin using milk samples from 341 and 663 Danish Holstein cows, respectively. Additionally, we conducted whole-genome association analysis to identify SNP and genes associated with vitamin B12 and transcobalamin. Our results indicated moderate to high heritability for vitamin B12 (0.37 ± 0.18) and transcobalamin (0.61 ± 0.13) content in the Danish Holstein. With a significance threshold of -log10 P-value > 5.87, significant associations were detected between SNP in Bos taurus autosome (BTA)17 and the log-transformed transcobalamin content of milk; no significant association was detected for vitamin B12. The significant region in BTA17 was imputed to full sequence for further fine mapping, and the SNP with the most significant associations to transcobalamin were assigned to the transcobalamin 2 (TCN2) gene.
RESUMO
We have used SAXS to determine the low-resolution structure of the outer-membrane protein OmpA from E. coli solubilized by the surfactant dodecyl maltoside (DDM). We have studied three variants of the transmembrane domain of OmpA-namely monomers, self-associated dimers, and covalently linked dimers-as well as the monomeric species of the full-length protein with the periplasmic domain. We can successfully model the structures of the monomeric and covalently linked dimer as one and two natively folded proteins in a DDM micelle, respectively, whereas the noncovalently linked dimer presents a more complicated structure, possibly due to higher-order species. We have determined the structure of the full-length protein to be that of a globular periplasmic domain attached through a flexible linker to the transmembrane domain. This approach provides valuable information about how membrane proteins are embedded in amphiphilic environments.