The vancomycin resistance gene clusters contain three general categories of genes, the core resistance proteins (VanHAX), the accessory proteins (VanJKWYZ and MurF2), and the sensor-regulator genes (VanRS). The regulator proteins include VanRS (and optionally VanU). These genes are part of a sensor-kinase two-component system. The VanO resistance cluster is similar to VanA and has an inverted VanHOX organization. Its terminal product is D-ala-D-lac.