Specific dimerization of the light chains of human immunoglobulin

Covalent dimerization of camelidae anti-human TNF-alpha single domain antibodies by the constant kappa light chain domain improves neutralizing activity

The tumor necrosis factor-alpha (TNFalpha) plays an important role in a number of chronic inflammatory disorders. Monoclonal camelidae variable heavy chain domain-only antibodies (V(H)H) have been developed to antagonize the action of human TNFalpha (anti-TNF-V(H)H). Here we describe a strategy to obtain functional dimeric anti-TNF-V(H)H molecules, based on the C-terminal fusion of a kappa light chain domain to the anti-TNF-V(H)H. The resulting fusion protein was transiently expressed by use of viral vectors in Nicotiana benthamiana((Nb)) leaves and purified. Competitive ELISA and cell cytotoxicity assays revealed that the dimerized anti-(Nb)TNF-V(H)H(Ckappa) proteins blocked TNFalpha-activity more effectively than either the monomeric Escherichia coli((Ec)) produced anti-(Ec)TNF-V(H)H or the monomeric anti-(Nb)TNF-V(H)H(Ckappa). We suggest that enhanced inhibition shown by dimeric anti-(Nb)TNF-V(H)H(Ckappa) proteins is achieved by an increase in avidity.

Effect of association state and conformational stability on the kinetics of immunoglobulin light chain amyloid fibril formation at physiological pH

Light chain amyloidosis involves the systemic deposition of fibrils in patients overproducing monoclonal immunoglobulin light chains. The kinetics of fibril formation of LEN, a benign light chain variable domain, were investigated at physiological pH in the presence of urea. Despite the lack of in vivo fibril formation, LEN readily forms fibrils in vitro under mildly destabilizing conditions. The effect of low to moderate concentrations of urea on the conformation, association state, stability, and kinetics of fibrillation of LEN were investigated. The conformation of LEN was only slightly affected by the addition of up to 4 m urea. The fibrillation kinetics were highly dependent on protein and urea concentrations, becoming faster with decreasing protein concentration and increasing urea concentration. Changes in spectral probes were concomitant to fibril formation throughout the protein and urea concentration ranges, indicating the absence of off-pathway oligomeric species or amorphous aggregates prior to fibril formation. Reducing the amount of dimers initially present in solution by either decreasing the protein concentration or adding urea resulted in faster fibril formation. Thus, increasing concentrations of urea, by triggering dissociation of dimeric LEN, lead to increased rates of fibrillation.

Three-dimensional structure of a hybrid light chain dimer: protein engineering of a binding cavity

An attempt was made to engineer a binding site and check its structure by X-ray analysis. Two human light chains (Mcg and Weir), with "variable" domain sequences differing in 36 positions, were hybridized into a heterologous dimer and crystallized in ammonium sulfate by the same procedure used for the trigonal form of the Mcg dimer. The three-dimensional structure of the hybrid was determined at 3.5-A resolution by difference Fourier analysis, interactive model building with computer graphics and crystallographic refinement. In the heterologous dimer, the Weir protein behaved as the structural analog of the heavy chain in an antigen binding fragment, while the Mcg protein assumed the role of the light chain component. The hybrid and the Mcg dimer were closely similar in overall structure, an observation probably correlated with the deliberate cleavage of the intrachain disulfide bond in the variable domain of the Weir protein during the hybridization procedure. Examination of the crystal structure of the hybrid suggested that the cleavage resulted in the relaxation of restraints which might otherwise have interfered with the formation of an Mcg-like dimer. There were six substitutions among the residues lining the binding cavities of the hybrid and Mcg dimer. These substitutions significantly affected the sizes, shapes and binding properties of the two cavities.

Monoclonal immunoglobulin light chains in urine of patients with lymphoma

Fourteen of 31 patients with non-Hodgkin's lymphoma or chronic lymphocytic leukaemia had a monoclonal immunoglobulin light chain detectable in their urine. These chains are believed to be synthesized by the B lymphoid cells comprising the tumour. Upon comparing the different cases, the occurrence and amount of monoclonal light chain showed no dependence upon the extent of tumour, the presence of leukaemic component, or exposure to cytotoxic therapy. The method of detection involved purifying the urinary light chains by immunosorption, and examining their electrophoretic distributions so as to distinguish between the homogeneous monoclonal chains and their heterogeneous normal analogues.

Kinetics of dimerization of the Bence-Jones protein Au

The dimerization reactions of complete Bence-Jones protein Au (VC-Au) and of its variable fragment (V-Au) were compared in 0.2 M (ionic strength) sodium phosphate buffer, pH 6.8 at 20 degrees C. The dimerization constant for VC-Au (6.6 X 10(4) M-1) was slightly smaller than a previously published value for the fragment (1.1 X 10(5) M-1). The reaction enthalpies were positive for both processes. Temperature jump experiments exhibited two kinetic phases. The relaxation time of the fast phase as well as its concentration dependence and amplitude were almost identical for VC-Au and V-Au. Only small differences were observed in the slow phase. These close similarities between the reactions of the two proteins demonstrate that dimerization occurs mainly via interactions between the variable domains and that the constant domains interfere very little. From the observation of two relaxation times it follows that the dimerization mechanism for both VC-Au and A-Au must include at least three reacting species. Mechanisms with an isomerization between monomers in two conformational states and a single dimer species are excluded by the data. Alternative mechanisms with a single monomeric species but isomerization between dimers give a rather unsatisfactory fit. A good fit can be obtained if it is assumed that both monomers and dimers can exist in two states. Rate constants of the association and dissociation steps are of the order of 10(7) M-1 s-1 and 10(2) s-1. Isomerization rate constants are in the range of 10 s-1.

On the isolation, characterisation, and crystallisation of a human Bence-Jones protein of kappa type

The isolation and purification of the human Bence-Jones protein Rei is described. Physico-chemical data are given characterising the protein. It is shown that the protein could be crystallised. It is intended to use the crystals for single crystal X-ray diffraction studies.

The recombination of dimers of immunoglobulin peptide chains

1. Both the gamma and light peptide chains of human pooled and myeloma immunoglobulin G can be prepared as non-aggregating dimers at pH5.4 in 4mm-sodium acetate buffer. The dimeric state is maintained by non-covalent bonds, since the formation of interchain disulphide bonds was prevented by alkylation of the thiol groups. In the case of the light chains there is some evidence that the dimers are in equilibrium with a small amount of monomer. 2. When such dimers of the gamma and light chains are mixed at pH5.4 in 4mm-sodium acetate buffer they combine rapidly, yielding a product that resembles the original immunoglobulin G in its physicochemical and antigenic properties. However, the original optical rotatory dispersion spectrum was regained only with the homogeneous myeloma protein. The recombined pooled immunoglobulin G had a spectrum slightly different from the original, suggesting that at least some of the recombinant molecules had not regained native conformations. 3. Dimers of gamma chains stabilized by interchain disulphide bonds were able to recombine with light chains. However, light chains stabilized in the dimeric state by interchain disulphide bonds would not combine with gamma chains. 4. The chains of rabbit immunoglobulin G behave similarly to the human chains in this system, apart from the alkylated light chains showing clearer evidence of monomeric components.

Synthesis and assembly of immunoglobulins by malignant human plasmacytes. I. Myelomas producing gamma-chains and light chains

Three basic patterns of gamma-globulin synthesis are described in malignant human plasmacytes: extreme unbalanced synthesis where only L chains are synthesized; unbalanced synthesis in which intact gammaG globulin and an excess of free L chains are synthesized and secreted; and balanced synthesis where H and L chains appear to be synthesized in equimolar amounts. Studies of the cellular products appear to reflect the biosynthetic processes of the cells in a more reliable fashion than does analysis of serum or urinary proteins. The absence of Bence Jones proteins from the urine does not necessarily indicate that free L chains are not being synthesized and secreted at the cellular level. Similarly, the completed globulin molecule secreted by malignant plasma cells may not be demonstrable by examination of serum. Patterns of globulin synthesis in human myelomatous tissues vary as do patterns of globulin synthesis in mouse plasmacytomas. Pulse-chase studies of the cells from one patient showed that a gammaG myeloma protein was assembled via an HL (half molecule) intermediate.

Subunits of Tamm-Horsfall glycoprotein

1. The effect of 6m-guanidine hydrochloride on the urinary glycoprotein described by Tamm & Horsfall (1952) is to produce a homogeneous subunit of molecular weight approx. 100000. 2. Complete reduction of the disulphide bonds of this subunit does not decrease the molecular weight, suggesting that all disulphide bonds are intrachain. 3. Comparison of sedimentation and viscometric behaviour of unreduced and reduced material in 6m-guanidine hydrochloride is consistent with reduction causing an opening-up of intrachain disulphide bonds to give a more asymmetric molecule.