TY  - JOUR
A1  - Burkhardt, Janin
A1  - Vonck, Janet
A1  - Averhoff, Beate
T1  - Structure and function of PilQ, a secretin of the DNA transporter from the thermophilic bacterium Thermus thermophilus HB27
T2  - Journal of biological chemistry
N2  - Secretins are a family of large bacterial outer membrane protein complexes mediating the transport of complex structures, such as type IV pili, DNA and filamentous phage, or various proteins, such as extracellular enzymes and pathogenicity determinants. PilQ of the thermophilic bacterium Thermus thermophilus HB27 is a member of the secretin family required for natural transformation. Here we report the isolation, structural, and functional analyses of a unique PilQ from T. thermophilus. Native PAGE, gel filtration chromatography, and electrophoretic mobility shift analyses indicated that PilQ forms a macromolecular homopolymeric complex that binds dsDNA. Electron microscopy showed that the PilQ complex is 15 nm wide and 34 nm long and consists of an extraordinary stable "cone" and "cup" structure and five ring structures with a large central channel. Moreover, the electron microscopic images together with secondary structure analyses combined with structural data of type II protein secretion system and type III protein secretion system secretins suggest that the individual rings are formed by conserved domains of alternating α-helices and β-sheets. The unprecedented length of the PilQ complex correlated well with the distance between the inner and outer membrane of T. thermophilus. Indeed, PilQ was found immunologically in both membranes, indicating that the PilQ complex spans the entire cell periphery of T. thermophilus. This is consistent with the hypothesis that PilQ accommodates a PilA4 comprising pseudopilus mediating DNA transport across the outer membrane and periplasmic space in a single-step process.
KW  - DNA Transformation
KW  - Membrane Proteins
KW  - Protein DNA-Interaction
KW  - Protein Purification
KW  - Protein Structure
KW  - Thermus thermophilus
KW  - Electron Microscopy
KW  - Membrane Protein Complex
KW  - Secretin
Y1  - 2021
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/76577
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-765774
SN  - 0021-9258
VL  - 286.2011
IS  - 12
SP  - 9977
EP  - 9984
PB  - American Society for Biochemistry and Molecular Biology Publications
CY  - Bethesda, Md
ER  -