Required for wild-type expression of ArfA and ammonia secretion, not however part of an ammonia transporter. Part of the arfA-arfB-arfC operon. Maximal expression of ArfA requires the full operon. Upon operon disruption no reduction of serine uptake at pH 6.9, no visible effect on outer membrane permeability, however severe delays in ammonia secretion, medium pH neutralization and growth also occur at pH 5.5. Belongs to the ArfC membrane protein family.