This serine-rich protein belongs to a family with large size (over 1000 amino acids), which a highly serine-rich central region that averages over 300 aa in length. Species encoding members of this family of proteins tend to be anaerobic bacteria, including Gram-positive bacteria of the human gut microbiome and Chloroflexi from marine sediments.
Jiyao W et al.(2023). "The conserved domain database in 2023.",