Recombinant Protein L

Cat: 11044-H07E

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Quality Assurance
Purity > 95% by SDS-PAGE Protein L
Expression System: E coli.
Molecular Mass: 39kD
Form: Liquid or lyophilized
Storage: -20℃ or below
Concentration: Refer to the label on the vial
   
Note: It is recommended that the protein be aliquoted and be used as soon as possible. Avoid repeated freeze-thaw cycles.
 
Source

Protein L was first isolated from the surface of bacterial species Peptostreptoccus magnus and was found to bind Ig through L chain interaction, from which the name was suggested[1].

 
Structure

Protein L consists of 719 amino acid residues[2] with a PI of 4.0[4]. The molecular weight of Protein L purified from the cell walls of Peptostreptoccus magnus was first estimated as 95kD by SDS-PAGE in the presence of 2-mercaptoethanol, while the molecular weight was determined to 76kD by gel chromatography in the presence of 6 M guanidine HCl. Protein L does not contain any interchain disulfide loops, nor does it consist of disulfide-linked subunits.

 
Affinity
Different from protein A and protein G, protein L binds predominantly to kappa light chains[5], without interfering with the antigen-binding site[3]. Among the four major VL subgroups of human κ chains, κI, κIII, and κIV, but not κII, light chains bind to protein L and that this interaction involves exclusively the VL portion of the molecule. Further, this interaction is conformationally dependent and requires the complete VL domain[6]. The interaction of protein L with Ig of various species is different. Bovine, dog and chicken IgG did not bind protein L. It was found that not all murine kappa light chains bind to protein L. Protein L reacted strongly with human, baboon, guinea pig, mouse, rat and pig IgG, and weakly with rabbit, horse and goat IgG[8]. antibody structure
 
Genetics
 

The gene for protein L contains five components: a signal sequence of 18 amino acids; a NH2-terminal region (“A”) of 79 residues; five homologous “B” repeats of 72-76 amino acids each; a COOH terminus region of two additional “C” repeats (52 amino acids each); a hydrophilic, proline-rich putative cell wall-spanning region (“W”) after the C repeats; a hydrophobic membrane anchor (“M”). Four of B repeats (36kD) were found to be responsible for the interaction with Ig light chains[2].

 
Application

Since the interaction between Protein L and Ig is with the light chain, it will bind to Ig of all classes. Therefore, it possesses the potential of being a universal Ig ligand. The unique ability of protein L to bind to the kappa light chains of antibodies makes it valuable in detection and purification of antibodies and antibody fragments that contain kappa light chains but not the Fc region, such as antigen-binding VL domains and Fv fragments prepared from monoclonal antibodies or produced in recombinant DNA systems. The isolation of mouse IgG1-class antibodies would be best performed with protein L.

 
IgG binding of protein A, G, and L
Species

Protein A

Protein G

Protein L

 Human

 IgG

+++

+++

+++

 

 IgG1

++++

++++

++++

 

 IgG2

++++

++++

++++

 

 IgG3

-

+++

+++

 

 IgG4

++++

++++

++++

 

 IgA

+

-

+++

 

 IgA1

+

-

+++

 

 IgA2

+

-

+++

 

 IgD

-

-

+++

 

 IgE

++

-

+++

 

 IgM

+

-

+++

 Rabbit

 IgG

+++

+++

+

 Cow

 IgG

+

+++

-

 

 IgG1

+

+++

-

 

 IgG2

+++

+++

-

 Cat

 IgG

+++

+

?

 Horse    

 IgG

++

++++

?

 Goat

 IgG

+

++

-

 

 IgG1

+

+++

-

 

 IgG2

+++

+++

-

 Guinea-pig

 IgG1

++

+

?

 

 IgG2

++

+

?

 Sheep

 IgG

+

++

-

 

 IgG1

+

++

-

 

 IgG2

+++

+++

-

 Dog

 

++

+

?

 Pig

 

+++

++

+++

 Rat

 IgG

+

++

+++

 

 IgG1

-

+

+++

 

 IgG2a

-

++++

+++

 

 IgG2b

-

++

+++

 

 IgG2c

++

++

+++

 

 IgG3

+

++

?

 Mouse

 IgG

++

++

+++

 

 IgG1

+

++++

+++

 

 IgG2a

++++

++++

+++

 

 IgG2b

+++

+++

+++

 

 IgG3

++

+++

+++

 

 IgM

-

-

+++

 Chicken

 IgY

-

-

-

 Monkey(rhesus)

 IgG

++++

++++

?

 Hamster

 

+

++

+++

 Koala

 

-

+

?

 Llama

 

-

+

?

 

Strong binding ++, medium interaction

Other Proteins

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