The Antibody Light-Chain Linker Regulates Domain Orientation and Amyloidogenicity

Abstract

The antibody light chain (LC) consists of two domains and is essential for antigen binding in mature immunoglobulins. The two domains are connected by a highly conserved linker which comprises the structurally important Arg108 residue. In antibody light chain (AL) amyloidosis, a severe protein amyloid disease, the LC and its N-terminal variable domain (VL) convert to fibrils deposited in the tissues causing organ failure. Understanding the factors shaping the architecture of the LC, is important for basic science, biotechnology and for deciphering the principles that lead to fibril formation. In this study, we examined the structure and properties of LC variants with a mutated or extended linker. We show that under destabilizing conditions, the linker modulates the amyloidogenicity of the LC. The fibril formation propensity of LC linker variants and their susceptibility to proteolysis directly correlate implying an interplay between the two LC domains. Using NMR and RDC-based simulations, we found that the linker residue Arg108 is a key factor regulating the relative orientation of the VL and CL domains, keeping them in a bent and dense, but still flexible conformation. Thus, inter-domain contacts and the relative orientation of VL and CL to each other are of major importance for maintaining the structural integrity of the full-length LC.

Breakdown of supersaturation barrier links protein folding to amyloid formation

“…3). These results were consistent with the previously reported high and low amyloidogenicity of V L 18 and C L 19 , respectively.…”

“…We first examined proteins with an immunoglobulin fold-like β 2 -microglobulin (β2m), a blood protein responsible for dialysis-related amyloidosis: the variable (V L ) 3,18 and constant (C L ) 19 domains of the immunoglobulin light chain. An excess amount of specific variants of monoclonal light chains or V L fragments secreted into the blood stream forms amyloids causing AL amyloidosis, whereas the C L domain is assumed to modulate V L 's amyloidogenicity 3,18,20 . At pH 7.0, upon heating under stirring, V L (PAT-1) exhibited an increase in ThT fluorescence at approximately 65°C, whereas no reaction was observed without stirring (Fig.…”

Effect of Single Amino Acid Substitutions by Asn and Gln on Aggregation Properties of Bence-Jones Protein BIF

“…The choice of mutations D29Q, S157Q and K170N was based on the empirical rule that the amyloid-prone region has to be located in a structurally disordered region, allowing its self-assembly without the necessity of conformational unfolding [7]. The Arg109 is important for the stabilization of C L domain [8,9]. Therefore, the substitution of Arg109 by Asn could be crucial and could facilitate the formation of fibrils.…”

Data-Driven Molecular Dynamics: A Multifaceted Challenge

“…Backbone chemical shifts were also used by Buckle et al to investigate the interaction of the SNa15 peptide with non-native mineral surfaces [144]. Finally, concerning NMR, RDC data were employed in the metainference framework by Weber and coworkers to study the conformational space accessible to the LC protein [145]. Interestingly, cryo-EM experimental data were demonstrated to suitable to be integrated in a metainference scheme.…”