ATP-binding (A) component of a common energy-coupling factor (ECF) ABC-transporter complex. Unlike classic ABC transporters this ECF transporter provides the energy necessary to transport a number of different substrates. In this organism these probably include biotin, thiamine precursor, niacin, pantothenic acid, queuosine precursor, riboflavin and thiamine. Uptake of niacin or riboflavin into proteosomes containing EcfA1A2T and Niax or RibU has been demonstrated. Uptake requires hydrolyzable Mg-ATP and is substrate-specific; NiaX-containing proteosomes did not transport riboflavin. Forms a stable energy-coupling factor (ECF) transporter complex composed of 2 membrane-embedded substrate-binding proteins (S component), 2 ATP-binding proteins (A component) and 2 transmembrane proteins (T component). In L.lactis forms a stable complex with EcfA' and EcfT and substrate-binding components. In E.coli forms a stable complex with EcfA', EcfT and individually with 3 tested substrate-binding components (BioY, NiaX and ThiT) with a stoichiometry of 1.1:1:1. The core ECF complex interacts with a number of substrate-specific binding components, including BioY, BioY2, HmpT, NiaX, PanT, QueT, RibU and ThiT. Belongs to the ABC transporter superfamily. Energy-coupling factor EcfA family.