Members of this family are found in the N terminal region of cytochrome B561, as well as in various other putative uncharacterised proteins.

1: Structural basis for the electron transfer across the chromaffin vesicle membranes catalyzed by cytochrome b561: analyses of cDNA nucleotide sequences and visible absorption spectra. Okuyama E, Yamamoto R, Ichikawa Y, Tsubaki M; Biochim Biophys Acta. 1998;1383:269-278. PMID:9602148