The structural abnormality of myeloma immunoglobulins tested by Congo red binding.
BACKGROUND
Frequently observed structural deviations of myeloma-derived immunoglobulins affect polypeptide chain packing and domain stability, enhancing their tendency to aggregate, with all the clinical consequences. Congo red complexation with myeloma immunoglobulins is proposed in this work as a general test to disclose the instability of these proteins. The large ribbon-like supramolecular ligands of Congo red form complexes with proteins by adhesion to beta-conformation polypeptide chains, if allowed to make contact with their backbone interfaces. This can occur in the case of myeloma-derived immunoglobulins with deficient polypeptide chain packing.


METHODS
Specially adapted two-dimensional agarose electrophoresis of serum proteins, which allows the transient contact of Congo red and serum proteins during migration, was used to reveal the presence of protein components amenable to ligand penetration and binding. The combination of electrophoresis and Congo red binding to proteins permits the removal of loosely attached dye and evaluation of the effective complexation properties of the immunoglobulin fraction directly in the serum.


RESULTS
Comparative studies of dye complexation with two L chains having different reactivities with Congo red confirmed that dye binding depended on protein instability in the conditions used. Myeloma proteins revealed different binding capabilities in the test used here.


CONCLUSIONS
The complexes formed by the supramolecular dye Congo red with myeloma immunoglobulins differ in stability. Those of high stability indicate the abnormal protein structure thought to produce clinical symptoms. This work proposes an easy technique to differentiate the stability of complexes.
Spólnik
Paweł
P
Institute of Medical Biochemistry, Collegium Medicum, Jagiellonian University, Cracow, Poland.
Piekarska
Barbara
B
Stopa
Barbara
B
Konieczny
Leszek
L
Zemanek
Grzegorz
G
Rybarska
Janina
J
Król
Marcin
M
Nowak
Mateusz
M
Roterman
Irena
I
D000595:Amino Acid Sequence; D004396:Coloring Agents / Q000378:metabolism*; D003198:Computer Simulation; D003224:Congo Red / Q000378:metabolism*; D015180:Electrophoresis, Gel, Two-Dimensional; D006801:Humans; D007146:Immunoglobulin lambda-Chains / Q000737:chemistry; D007136:Immunoglobulins / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D009194:Myeloma Proteins / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation; D013194:Staining and Labeling; D013696:Temperature
D004396:Coloring Agents; D007146:Immunoglobulin lambda-Chains; D007136:Immunoglobulins; D008024:Ligands; D009194:Myeloma Proteins; C017551:myeloma immunoglobulins; D003224:Congo Red