Bioinformatic analyses of a putative zinc periplasmic metallochaperone in Pseudomonas aeruginosa

PAULA MIHELJ; DANIEL RAIMUNDA

Congreso; Biofísica en tiempos de COVID-19 : Primeras Jornadas Virtuales SAB 2020; 2020

Zinc (Zn2+) is fundamental in almost all living organisms participating as enzyme co-factor and signaling pathways. Several Zn2+ transporters families allocate the metal intracellularly for proper storage and protein metalation, or extracellularly to avoid accumulation and toxicity. In Pseudomonas aeruginosa, YiiP, a member of the Cation Diffusion Facilitator (CDF) family, exports Zn2+ from the cytosol to the periplasm. Due to the in-transit toxicity of Zn2+, we hypothesize that YiiP transport activity is assisted by cytosolic and/or periplasmic metallochaperones, giving or receiving the metal respectively. Up-stream the yiip/PA3963 gene, the locus PA3962, is classified as ahypothetical protein with unknown function and structure. A BLAST search for bacterial homologs, points that this protein is unique to the Pseudomonadales clade. Bioinformatic structural analyses, using the threading tool I-TASSER, showed that PA3962 has a structural similarity with CopZ, a Cu+ metallochaperone from Bacillus subtilis. At the primary sequence level using LipoP, we identified in PA3962 a lipobox motif conserved in lipoproteins processed by Signal Peptidase II. Zn2+ quantification by atomic absorption spectroscopy in cellular fractions of P. aeruginosa WT and the insertional mutant strain PA3962::Tn5 indicates increased Zn2+ levels in the inner membranes of PA3962::Tn5 vs.WT, but not in other fractions. Considering all the evidences gathered, we propose a working model where PA3962 plays a role as a periplasmic metallochaperone located at the inner membrane coordinating in-transit Zn2+.