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AL amyloidosis (AL) results from the misfolding of immunoglobulin light chains (IG LCs). Aim of this study was to comprehensively analyse kappa LC sequences from AL patients in comparison with multiple myeloma (MM). We analysed IGKV/IGKJ usage and associated organ tropism and IGKV1/D-33 in terms of mutational analysis and theoretical biochemical properties. cDNA and bulk RNA sequencing of the LCs of AL and MM patients. We studied 41 AL and 83 MM patients showing that IGKV1 was most expressed among kappa AL and MM, with higher frequency in AL (80% vs. 53%, p =.002). IGKV3 was underrepresented in AL (10% vs. 30%, p =.014). IGKJ2 was more commonly used in AL than in MM (39% vs. 29%). Patients with IGKV1/D-33 were associated with heart involvement (75%, p =.024). IGKV1/D-33-segments of AL had a higher mutation count (AL = 12.0 vs. MM = 10.0). FR3 and CDR3 were most frequently mutated in both, with a median mutation count in FR3 being the highest (AL = 4.0; MM = 3.5) and one mutation hotspot (FR3 (83I)) for IGKV1/D-33/IGKJ2 was associated with cardiac involvement. This study confirmed that germline usage has an influence on AL amyloidosis risk and organ involvement. [ABSTRACT FROM AUTHOR]

Systemic AL amyloidosis arises from the misfolding of patient-specific immunoglobulin light chains (LCs). Potential drivers of LC amyloid formation are mutational changes and post-translational modifications (PTMs). However, little information is available on the exact primary structure of the AL proteins and their precursor LCs. We analyse the exact primary structure of AL proteins extracted from 10 λ AL amyloidosis patients and their corresponding precursor LCs. By cDNA sequencing of the precursor LC genes in combination with mass spectrometry of the AL proteins, the exact primary structure and PTMs were determined. This information was used to analyse their biochemical properties. All AL proteins comprise the VL and a small part of the CL with a common C-terminal truncation region. While all AL proteins retain the conserved native disulphide bond of the VL, we found no evidence for presence of other common PTMs. The analysis of the biochemical properties revealed that the isoelectric point of the VL is significantly increased due to introduced mutations. Our data imply that mutational changes influence the surface charge properties of the VL and that common proteolytic processes are involved in the generation of the cleavage sites of AL proteins. [ABSTRACT FROM AUTHOR]

Summary: Acetogenic bacteria are a group of strictly anaerobic bacteria that may have been first life forms on Earth since they employ an ancient pathway for CO2 fixation into acetyl‐CoA that is coupled to the synthesis of ATP, the Wood–Ljungdahl pathway. Electrons for CO2 reduction are derived from oxidation of H2 or CO and thus, these bacteria can grow lithotrophically on gases present on early Earth. Among the organic molecules present on early Earth is acetaldehyde, a highly volatile C2 compound. Here, we demonstrate that the acetogenic model bacterium Acetobacterium woodii grows on acetaldehyde. Acetaldehyde is dismutated to ethanol and acetyl‐CoA, most likely by the bifunctional alcohol dehydrogenase AdhE. Acetyl‐CoA is converted to acetate by two subsequent enzymes, phosphotransacetylase and acetate kinase, accompanied by the synthesis of ATP by substrate‐level phosphorylation. Apparently, growth on acetaldehyde does not employ the Wood–Ljungdahl pathway. Our finding opens the possibility of a simple and ancient metabolic pathway with only three enzymes that allows for biomass (acetyl‐CoA) and ATP formation on early Earth. [ABSTRACT FROM AUTHOR]