Thermodynamic stability of a kappaI immunoglobulin light chain: relevance to multiple myeloma.
Immunoglobulin light chains have two similar domains, each with a hydrophobic core surrounded by beta-sheet layers, and a highly conserved disulfide bond. Differential scanning calorimetry and circular dichroism were used to study the folding and stability of MM-kappaI, an Ig LC of kappaI subtype purified from the urine of a multiple myeloma patient. The complete primary structure of MM-kappaI was determined by Edman sequence analysis and mass spectrometry. The protein was found to contain a cysteinyl post-translational modification at Cys(214). Protein stability and conformation of MM-kappaI as a function of temperature or denaturant conditions at pH 7.4 and 4.8 were investigated. At pH 4.8, calorimetry demonstrated that MM-kappaI undergoes an incomplete, cooperative, partially reversible thermal unfolding with increased unfolding temperature and calorimetric enthalpy as compared to pH 7.4. Secondary and tertiary structural analyses provided evidence to support the presence of unfolding intermediates. Chemical denaturation resulted in more extensive protein unfolding. The stability of MM-kappaI was reduced and protein unfolding was irreversible at pH 4.8, thus suggesting that different pathways are utilized in thermal and chemical unfolding.
Chung
Connie M
CM
Department of Physiology and Biophysics, Boston University School of Medicine, Massachusetts, 02118, USA.
Chiu
Jenny D
JD
Connors
Lawreen H
LH
Gursky
Olga
O
Lim
Amareth
A
Dykstra
Andrew B
AB
Liepnieks
Juris
J
Benson
Merrill D
MD
Costello
Catherine E
CE
Skinner
Martha
M
Walsh
Mary T
MT
D000595:Amino Acid Sequence; D055592:Biophysical Phenomena; D001703:Biophysics; D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D004355:Drug Stability; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007145:Immunoglobulin kappa-Chains / Q000737:chemistry* / Q000235:genetics; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D009101:Multiple Myeloma / Q000235:genetics / Q000276:immunology*; D011487:Protein Conformation; D011489:Protein Denaturation; D017434:Protein Structure, Tertiary; D013816:Thermodynamics
D007145:Immunoglobulin kappa-Chains