Type III secretion effectors in bacterial genome
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Transcript of Type III secretion effectors in bacterial genome
Type III secretion effectors in Type III secretion effectors in bacterial genomebacterial genome
5 May 20105 May 2010
Sūn Guăng Wén Sūn Guăng Wén
Biochemistry, NUSBiochemistry, NUS
MelioidosisMelioidosis Causative agent: Causative agent: Burkholderia Burkholderia
pseudomalleipseudomallei Endemic area: SEA; northern AustraliaEndemic area: SEA; northern Australia Symptom: variableSymptom: variable Diagnosis: Serum test, culture of bacteria, Diagnosis: Serum test, culture of bacteria,
PCRPCR Risk factor: Type II diabetes and kidney Risk factor: Type II diabetes and kidney
failurefailure Treatment: CeftazidimeTreatment: Ceftazidime Vaccine: not available Vaccine: not available
Burkholderia pseudomalleiBurkholderia pseudomallei
• Facultative anaerobic,
in soil and surface water• Opportunistic pathogen• Resistant to many antibiotics• Huge genome: 4.1Mb +3.2Mb
• Many virulence factors: siderophore, flagella, T3SSs, T6SSs
• Able to invade cells and survive intracellularly
Type III secretion system Type III secretion system (T3SS)(T3SS)
SPI I of Salmonella
T3SS and flagellaT3SS and flagella
Distribution of T3SSs among pathogenic bacteria
Nat rev MCB 3:743
T3 Effectors modify host signaling T3 Effectors modify host signaling pathwayspathways
Effectors mimic host protein Effectors mimic host protein functionfunction
Effectors can introduce Effectors can introduce covalent-modificationcovalent-modification
Effectors are less conservedEffectors are less conserved
N-terminal of effector contains N-terminal of effector contains secretion signalsecretion signal
Fusion assay N-ter signal reporter
Determination of secretion signalDetermination of secretion signal
PLoS Pathogens April 2009 | Volume 5 | Issue 4 | e1000376
http://www.effectors.org/ ---very high false positive rate!
Signal is more defined within a Signal is more defined within a speciesspecies
Inv/mxi/spa-like T3S3 ofInv/mxi/spa-like T3S3 of B. B. pseudomalleipseudomallei
Base and inner membrane complex
TransloconsSecreted effectors
Molecular Microbiology (2002) 46(3), 649–659
Molecular Microbiology (2010) 76(3), 677–689
Regulator
Chaperone
Burkholderia pseudomalleiBurkholderia pseudomallei genomegenome
Burkholderia pseudomallei K96243: NC_006350; NC_006351 ,
http://www.ncbi.nlm.nih.gov/sutils/genom_table.cgihttp://www.sanger.ac.uk/cgi-bin/blast/submitblast/b_pseudomallei
The challenge: To identify T3S3 The challenge: To identify T3S3 effectors ineffectors in bp bp genomes genomes
Define training sets, collect effector Define training sets, collect effector sequencessequences
Find patterns in N-terminalsFind patterns in N-terminals Search Search Burkholderia pseudomalleiBurkholderia pseudomallei
genomesgenomes Blast top hits in protein databasesBlast top hits in protein databases Verify through experimentsVerify through experiments
Assembly of T3S needleAssembly of T3S needle