TY - JOUR

T1 - PcoB is a defense outer membrane protein that facilitates cellular uptake of copper

AU - Li, Ping

AU - Nayeri, Niloofar

AU - Górecki, Kamil

AU - Becares, Eva Ramos

AU - Wang, Kaituo

AU - Mahato, Dhani Ram

AU - Andersson, Magnus

AU - Abeyrathna, Sameera S.

AU - Lindkvist-Petersson, Karin

AU - Meloni, Gabriele

AU - Missel, Julie Winkel

AU - Gourdon, Pontus

N1 - Publisher Copyright: © 2022 The Authors. Protein Science published by Wiley Periodicals LLC on behalf of The Protein Society.

PY - 2022

Y1 - 2022

N2 - Copper (Cu) is one of the most abundant trace metals in all organisms, involved in a plethora of cellular processes. Yet elevated concentrations of the element are harmful, and interestingly prokaryotes are more sensitive for environmental Cu stress than humans. Various transport systems are present to maintain intracellular Cu homeostasis, including the prokaryotic plasmid-encoded multiprotein pco operon, which is generally assigned as a defense mechanism against elevated Cu concentrations. Here we structurally and functionally characterize the outer membrane component of the Pco system, PcoB, recovering a 2.0 Å structure, revealing a classical β-barrel architecture. Unexpectedly, we identify a large opening on the extracellular side, linked to a considerably electronegative funnel that becomes narrower towards the periplasm, defining an ion-conducting pathway as also supported by metal binding quantification via inductively coupled plasma mass spectrometry and molecular dynamics (MD) simulations. However, the structure is partially obstructed towards the periplasmic side, and yet flux is permitted in the presence of a Cu gradient as shown by functional characterization in vitro. Complementary in vivo experiments demonstrate that isolated PcoB confers increased sensitivity towards Cu. Aggregated, our findings indicate that PcoB serves to permit Cu import. Thus, it is possible the Pco system physiologically accumulates Cu in the periplasm as a part of an unorthodox defense mechanism against metal stress. These results point to a previously unrecognized principle of maintaining Cu homeostasis and may as such also assist in the understanding and in efforts towards combatting bacterial infections of Pco-harboring pathogens.

AB - Copper (Cu) is one of the most abundant trace metals in all organisms, involved in a plethora of cellular processes. Yet elevated concentrations of the element are harmful, and interestingly prokaryotes are more sensitive for environmental Cu stress than humans. Various transport systems are present to maintain intracellular Cu homeostasis, including the prokaryotic plasmid-encoded multiprotein pco operon, which is generally assigned as a defense mechanism against elevated Cu concentrations. Here we structurally and functionally characterize the outer membrane component of the Pco system, PcoB, recovering a 2.0 Å structure, revealing a classical β-barrel architecture. Unexpectedly, we identify a large opening on the extracellular side, linked to a considerably electronegative funnel that becomes narrower towards the periplasm, defining an ion-conducting pathway as also supported by metal binding quantification via inductively coupled plasma mass spectrometry and molecular dynamics (MD) simulations. However, the structure is partially obstructed towards the periplasmic side, and yet flux is permitted in the presence of a Cu gradient as shown by functional characterization in vitro. Complementary in vivo experiments demonstrate that isolated PcoB confers increased sensitivity towards Cu. Aggregated, our findings indicate that PcoB serves to permit Cu import. Thus, it is possible the Pco system physiologically accumulates Cu in the periplasm as a part of an unorthodox defense mechanism against metal stress. These results point to a previously unrecognized principle of maintaining Cu homeostasis and may as such also assist in the understanding and in efforts towards combatting bacterial infections of Pco-harboring pathogens.

KW - gut microbiota

KW - outer membrane protein structure

KW - PcoB

UR - http://www.scopus.com/inward/record.url?scp=85132935605&partnerID=8YFLogxK

U2 - 10.1002/pro.4364

DO - 10.1002/pro.4364

M3 - Journal article

C2 - 35762724

AN - SCOPUS:85132935605

VL - 31

SP - 1

EP - 16

JO - Protein Science

JF - Protein Science

SN - 0961-8368

IS - 7

M1 - e4364

ER -