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Table 2 Selection of different residues and results of slide agglutination assay using specific antisera to 3/4 O-acetylation against S. flexneri strains expressing different site-directed mutants of OacB

From: Identification of critical residues of O-antigen-modifying O-acetyltransferase B (OacB) of Shigella flexneri

S. flexneri

Residue mutated to Alanine

Location in OacB

Reason for mutation

Agglutination levela

Functionality

SFL1691

N/A

  

 

SFL1683

N/A

  

+++

Yes

SFL2591

D44

Cytoplasmic loop 2

Part of conserved Motif 1

+++

Yes

SFL2583

R47

Cytoplasmic loop 2

Part of conserved Motif 1

No

SFL2595

H58

TM II

Conserved in motif 1

No

SFL2584

W71

Periplasmic loop 3

Not conserved

No

SFL2596

V87

TM III

conserved

+++

Yes

SFL2588

Y96

TM III

Part of conserved motif 2

+++

Yes

SFL2589

F98

TM III

Part of conserved motif 2

No

SFL2585

R116

Cytoplasmic loop 4

Part of conserved motif 3

No

SFL2586

R119

Cytoplasmic loop 4

Part of conserved motif 3

No

SFL2593

P122

TM IV

Conserved

+++

Yes

SFL2620

S139

Periplasmic loop five

Not conserved

Charge and part of large loop five

+

Yes

SFL2619

G140

Periplasmic loop five

Not conserved part of large loop five

+++

Yes

SFL2617

S146

Periplasmic loop 5

Not conserved part of large loop five

No

SFL2621

S153

Periplasmic loop five

Not conserved part of large loop five

+

Yes

SFL2587

K156

Periplasmic loop 5

Polar not conserved

+++

Yes

SFL2618

G164

Periplasmic loop five

Not conserved

++

Yes

SFL2616

D173

Periplasmic loop five

Not conserved

+++

Yes

SFL2622

S174

Periplasmic loop five

Not conserved part of large loop five

+++

Yes

SFL2592

E188

TM V

Not conserved

+++

Yes

SFL2594

FY191–192

TM V

Not conserved

+++

Yes

SFL2597

WT183–184

TM V

Not conserved

+++

Yes

SFL2590

H320

TM X

Not conserved catalytic residue

+++

Yes

  1. aAgglutination levels were detected as being either strong (+ + +), medium (+ +), weak (+), or no agglutination (−). The absence of agglutination shows OacB is not functional or not present