Binds purine nucleosides and may play a role in purine nucleoside uptake. May be part of an ABC-type nucleoside uptake system. Has highest affinity for guanosine, followed by inosine and adenosine. Has very low affinity for cytidine and does not bind thymidine. Monomer. Encoded in an operon with TP_0320, TP_0321, TP_0322 and TP_0323 that may code for an ABC-type nucleoside uptake system, with TP_0322 and/or TP_0323 encoding putative permeases, and TP_0319 encoding a ligand-binding protein. Belongs to the BMP lipoprotein family.