Calcium binding by a myeloma protein

Am J Med. 1979 Aug;67(2):343-6. doi: 10.1016/0002-9343(79)90412-1.

Abstract

We describe a patient with immunoglobulin G (IgG)-kappa myeloma and severe, long-standing, asymptomatic hypercalcemia. Serum nonprotein-bound calcium concentration was 5.2 mg/dl (normal 4.2 to 5.0 mg/dl) at a time when total serum calcium concentration was 17.8 mg/dl. The patient's myeloma protein, IgGCAB, and Fab fragments of IgGCAB migrated more anodally when agarose gel electrophoresis was performed in the absence of calcium ion than when electrophoresis was performed in the presence of calcium ion; 60 other myeloma proteins did not demonstrate such behavior. Purified IgGCAB bound 1.5 calcium ions with a single dissociation constant of 1.2 X 10(-4) M. We speculate that the rare syndrome of myeloma and high protein-bound calcium is due to binding of calcium to variable regions of the myeloma antibody molecules.

Publication types

  • Case Reports

MeSH terms

  • Calcium / metabolism*
  • Humans
  • Hypercalcemia / etiology*
  • Hypercalcemia / metabolism
  • Immunoglobulin Fab Fragments / analysis
  • Immunoglobulin G / analysis
  • Immunoglobulin kappa-Chains / analysis
  • Male
  • Middle Aged
  • Multiple Myeloma / complications*
  • Multiple Myeloma / metabolism
  • Myeloma Proteins / metabolism*
  • Protein Binding

Substances

  • Immunoglobulin Fab Fragments
  • Immunoglobulin G
  • Immunoglobulin kappa-Chains
  • Myeloma Proteins
  • Calcium