May play a role in controlling magnetite number and size but not in control of magnetite morphology. Locus amb0973 is part of the probable 18 gene mamAB operon. When both copies of this protein are deleted cells have a weak magnetic response and make magnetosome membranes; the magnetosomes are less numerous and smaller. Deletion of just amb0973 leads to an intermediate magnetic response and still makes magnetosome membranes (PubMed:20212111). Deletion of genes mamH to mamV (amb0961 to amb0978) gives cells with no magnetosomes and no magnetic response (PubMed:20212111). This bacteria makes up to 20 cubo-octahedral magnetosomes of about 45 nm in diameter which contain membrane-bound crystals of magnetite (Fe(3)O(4)). Expression of just the minimal mamAB gene cluster (amb0961 to amb0978), including this gene, is sufficient to form a minimal magnetosome chain with small magnetite particles. Belongs to the magnetosome MamR family.