Figure 5. Human gut microbes likely encode at least 27 distinct corrinoid transporter families.
(A) Amino acid sequence identity from >80% of the length aligned between BtuB orthologs from B. thetaiotaomicron (BtuB1-BtuB3), E. coli K-12 (BtuB-Ec), and S. typhimurium LT2 (BtuB-St). (B) Rarefaction analysis on BtuB protein families as defined by a 50% amino acid identity cutoff. The mean number of BtuB families observed as increasing numbers of genomes are sampled is shown as a bold line; standard deviations from 100 permutations are shown with shading. See also Figure S5.