This family includes Tll0287 protein from Thermosynechococcus vestitus (Q8DM36) and similar bacterial proteins. Tll0287 is a c-type heme protein that shows a beta-sheet with four antiparallel beta-strands surrounded by five alpha-helices. This structure is similar to some kinases and sensor proteins, but its specific function is unknown [1].

1: Crystal structure and redox properties of a novel cyanobacterial heme protein with a His/Cys heme axial ligation and a Per-Arnt-Sim (PAS)-like domain. Motomura T, Suga M, Hienerwadel R, Nakagawa A, Lai TL, Nitschke W, Kuma T, Sugiura M, Boussac A, Shen JR; J Biol Chem. 2017;292:9599-9612. PMID:28428249