TY  - JOUR
AU  - Van der Meeren, R.
AU  - Wen, Y.
AU  - Van Gelder, P.
AU  - Tommassen, J.
AU  - Devreese, B.
AU  - Savvides, S. N.
AU  - DESY
TI  - New insights into the assembly of bacterial secretins: structural studies of the periplasmic domain of XcpQ from Pseudomonas aeruginosa
JO  - The journal of biological chemistry
VL  - 288
SN  - 0021-9258
CY  - Bethesda, Md.
PB  - Soc.
M1  - PHPPUBDB-25356
SP  - 1214-1225
PY  - 2013
AB  - The type II secretion system is a multiprotein assembly spanning the inner and outer membranes in Gram-negative bacteria. It is found in almost all pathogenic bacteria where it contributes to virulence, host tissue colonization, and infection. The exoproteins are secreted across the outer membrane via a large translocation channel, the secretin, which typically adopts a dodecameric structure. These secretin channels have large periplasmic N-terminal domains that reach out into the periplasm for communication with the inner membrane platform and with a pseudopilus structure that spans the periplasm. Here we report the crystal structure of the N-terminal periplasmic domain of the secretin XcpQ from Pseudomonas aeruginosa, revealing a two-lobe dimeric assembly featuring parallel subunits engaging in well defined interactions at the tips of each lobe. We have employed structure-based engineering of disulfide bridges and native mass spectrometry to show that the periplasmic domain of XcpQ dimerizes in a concentration-dependent manner. Validation of these insights in the context of cellular full-length XcpQ and further evaluation of the functionality of disulfide-linked XcpQ establishes that the basic oligomerization unit of XcpQ is a dimer. This is consistent with the notion that the dodecameric secretin assembles as a hexamer of dimers to ensure correct projection of the N-terminal domains into the periplasm. Therefore, our studies provide a key conceptual advancement in understanding the assembly principles and dynamic function of type II secretion system secretins and challenge recent studies reporting monomers as the basic subunit of the secretin oligomer.
KW  - Amino Acid Sequence
KW  - Bacterial Proteins: chemistry
KW  - Bacterial Proteins: genetics
KW  - Bacterial Proteins: metabolism
KW  - Electrophoresis, Polyacrylamide Gel
KW  - Mass Spectrometry
KW  - Molecular Sequence Data
KW  - Periplasm: metabolism
KW  - Protein Conformation
KW  - Pseudomonas aeruginosa: metabolism
KW  - Recombinant Proteins: chemistry
KW  - Recombinant Proteins: genetics
KW  - Recombinant Proteins: metabolism
KW  - Secretin: metabolism
KW  - Sequence Homology, Amino Acid
KW  - Bacterial Proteins (NLM Chemicals)
KW  - Recombinant Proteins (NLM Chemicals)
KW  - Secretin (NLM Chemicals)
LB  - PUB:(DE-HGF)16
C6  - pmid:23188826
C2  - pmc:PMC3543004
UR  - <Go to ISI:>//WOS:000313570300042
DO  - DOI:10.1074/jbc.M112.432096
UR  - https://bib-pubdb1.desy.de/record/141270
ER  -