Functions as both a transcriptional activator and repressor of multiple genes encoding virulence factors as well as genes involved in environmental adaptation (PubMed:16352829, PubMed:26549743, PubMed:22511872). Plays a role in alginate production via the activation of AlgD which is the first gene in the alginate biosynthetic operon (PubMed:16352829, PubMed:10476040). Regulates also the transcription of genes responsible for type IV pili localization and twitching motility (PubMed:16352829). Mediates transition of P.aeruginosa biofilm infections from colonizing to chronic biofilms through repression of the psl operon (PubMed:23354748). Represses also its own transcription by binding to two sites on amrZ promoter, amrZ1 and amrZ2 (PubMed:15968052). Forms homotetramers (via C-terminus). The C-terminal is essential for tetramerization as well as efficient AmrZ-mediated activation and repression of its targets. Deletion strain produces no detectable surface pili (PubMed:16352829). Abolishes also mucoidy and algD transcription (PubMed:10476040).