Zinc ABC transporter solute-binding lipoprotein AdcAII (AdcAII)

AdcAII, or Zinc ABC transporter solute-binding lipoprotein AdcAII, is a cell surface-exposed zinc-binding lipoprotein found in *Streptococcus pneumoniae* and related streptococcal species. It is one of two solute-binding proteins (the other being AdcA) that shuttle extracellular zinc ions to the AdcCB ATP-binding cassette transporter system, enabling the pathogen to survive and persist in zinc-depleted environments such as the human host. AdcAII is especially important during initial host colonization and invasive disease phases and is functionally linked to polyhistidine triad (Pht) proteins, which together cooperate in zinc recruitment. The protein’s structure has been resolved by X-ray crystallography and features a unique zinc-binding site crucial for high-affinity metal acquisition. Disruption of AdcAII function impairs zinc uptake, reduces virulence, and can lead to hyperencapsulation phenotypes, which influence resistance to immune clearance and disease severity. Due to its critical role in bacterial survival and absence in humans, AdcAII represents a promising target for the development of new antimicrobial therapies—especially those seeking to block metal ion uptake pathways in pathogens.

Other names

AdcAIIZinc-binding lipoprotein AdcAIIStreptococcus pneumoniae AdcAII

Prospective drugs would inhibit zinc binding or transport, thereby impairing the pathogen’s ability to acquire zinc, a metal essential for bacterial survival and virulence.