AlgK is a TPR-containing protein and the periplasmic component of a novel exopolysaccharide secretin.
The opportunistic pathogen Pseudomonas aeruginosa causes chronic biofilm infections in cystic fibrosis patients. During colonization of the lung, P. aeruginosa converts to a mucoid phenotype characterized by overproduction of the exopolysaccharide alginate. Here we show that AlgK, a protein essential for production of high molecular weight alginate, is an outer membrane lipoprotein that contributes to the correct localization of the porin AlgE. Our 2.5 A structure shows AlgK is composed of 9.5 tetratricopeptide-like repeats, and three putative sites of protein-protein interaction have been identified. Bioinformatics analysis suggests that BcsA, PgaA, and PelB, involved in the production and export of cellulose, poly-beta-1,6-N-Acetyl-D-glucosamine, and Pel exopolysaccharide, respectively, share the same topology as AlgK/E. Together, our data suggest that AlgK plays a role in the assembly of the alginate biosynthetic complex and represents the periplasmic component of a new type of outer membrane secretin that differs from canonical bacterial capsular polysaccharide secretion systems.
Molecular Structure and Function, Hospital for Sick Children, Toronto, ON M5G 1X8, Canada.
Carrie-Lynn
CL
Keiski
Michael
M
Harwich
Sumita
S
Jain
Ana Mirela
AM
Neculai
Patrick
P
Yip
Howard
H
Robinson
John C
JC
Whitney
Laura
L
Riley
Lori L
LL
Burrows
Dennis E
DE
Ohman
P Lynne
PL
Howell
D000464:Alginates; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D018441:Biofilms; D018360:Crystallography, X-Ray; D020723:Glucuronic Acid / Q000096:biosynthesis; D006603:Hexuronic Acids; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011135:Polysaccharides, Bacterial / Q000737:chemistry* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011550:Pseudomonas aeruginosa / Q000378:metabolism / Q000472:pathogenicity; D012633:Secretin
C104798:AlgK protein, Pseudomonas aeruginosa; D000464:Alginates; D001426:Bacterial Proteins; D006603:Hexuronic Acids; D011135:Polysaccharides, Bacterial; D012633:Secretin; D020723:Glucuronic Acid