Plasma membrane organization of the four protein domains of the main types of ABC transporters encountered in Porphyromonas gingivalis and organization of the chromosomal region containing the genes encoding one particular member. The membrane-spanning domains (MSDs) and the two nucleotide-binding domains (NBDs) are depicted by ovals and triangles, respectively. When fused, domains are linked together using a large connecting area. Arrows indicate genes and their direction of transcription The yellow arrows indicate solute-binding protein(SBP). The gene names are indicated below the arrows.