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Table 2 Fluorescence titration analysis of the salt-dependence of interaction between OASS and ligands

From: Comparative thermodynamic studies on substrate and product binding of O-Acetylserine Sulfhydrylase reveals two different ligand recognition modes†

 

Cysteine

Methionine

[NaCl] M

N

Qmax

Kobs (M-1)

ΔG (kJ/mol)

N

Qmax

Kobs (M-1)

ΔG (kJ/mol)

St OASS binding

        

0.02

2

3.8

6.0 ± 0.1 × 102

-15.0 ± 0.1

2

3.8

2.9 ± 0.1 × 102

-13.3 ± 0.1

0.05

2

4.6

5.6 ± 0.1 × 102

-14.9 ± 0.1

-

   

0.1

2

4.6

4.5 ± 0.1 × 102

-14.3 ± 0.1

2

1.0

6.5 ± 0.1 × 101

-10.0 ± 0.1

0.2

2

4.5

3.7 ± 0.1 × 102

-13.9 ± 0.1

2

1.4

5.5 ± 0.1 × 101

-9.4 ± 0.1

0.5

2

4.7

2.6 ± 0.1 × 102

-13.0 ± 0.1

2

0.5

3.5 ± 0.1 × 101

-8.7 ± 0.1

Hi OASS binding

        

0.02

2

3.9

6.6 ± 0.1 × 102

-15.2 ± 0.1

-

3.0

1.5 ± 0.1 × 102

-11.8 ± 0.2

0.05

2

5.7

5.6 ± 0.1 × 102

-15.5 ± 0.1

-

   

0.1

2

5.8

4.5 ± 0.1 × 101

-9.0 ± 0.1

2

0.5

5.8 ± 0.1 × 101

-9.5 ± 0.5

0.2

2

5.8

3.1 ± 0.1 × 101

-8.0 ± 0.1

2

0.2

3.4 ± 0.1 × 101

-8.1 ± 0.5

0.5

2

3.1

3.2 ± 0.1 × 101

-8.0 ± 0.1

2

0.2

2.3 ± 0.1 × 101

-7.3 ± 0.6

  1. Titrations were performed in 20 mM Tris buffer (pH 8.0), and indicated [NaCl]. Data were fit to a two independent sites binding model that yielded similar values of Kobs for each site.
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BMC Biochemistry

ISSN: 1471-2091

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