Binds L-arginine with high affinity. Shows no measurable affinity for L-ornithine. Part of the aot operon that encodes proteins involved in the uptake of arginine and ornithine. Expression of the aot operon is strongly induced by arginine, via the HTH-type transcriptional regulator ArgR. Deletion of the aotJQMOP genes greatly reduces arginine and ornithine uptake (PubMed:9791103). Disruption mutant has a reduced capacity to use arginine and ornithine as sole carbon source for growth (PubMed:18833300). Belongs to the bacterial solute-binding protein 3 family.