Nicolardi, S. | Search bioRxiv

bioRxiv2025

Replication of 10 novel loci involved in human plasma protein N-glycosylation using MALDI-MS and UHPLC-FD data

N-glycans are essential components of glycoproteins, influencing their properties and functions. While biochemical pathways of glycosylation are well-characterized, their genetic regulation remains poorly understood. This study utilizes matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) and ultra-high performance liquid chromatography-fluorescence detection (UHPLC-FD) to strengthen replication and further characterize previously identified genome-wide association signals for the total human plasma N-glycome (TPNG). Univariate and multivariate genetic association meta-analyses involved 3,385 samples across 143 N-glycome traits from the Hoorn Diabetes Care System and DiaGene cohorts as well as 3,224 samples across 117 N-glycome traits from TwinsUK, CEDAR, QMDiab and SABRE cohorts. We successfully replicated ten previously identified but not replicated glycosylation quantitative trait loci (glyQTLs) and prioritized five high-confidence putative causal genes, including the glycosyltransferase MGAT4B and inflammation-related genes - C3 and FCGR2B. The linkage-specific sialic acid derivatization in MALDI-MS enabled delineation of genetic effects on 2,3- and 2,6-sialylation. Mass spectrometry analysis also provided evidence for glucuronic acid-containing glycans in human blood plasma. These findings advance our understanding of the genetic regulation of protein N-glycosylation and highlight the complementarity of different analytical approaches in glycomics research.

genetics↗

bioRxiv2023

CslA and GlxA from Streptomyces lividans form a functional cellulose synthase complex

Filamentous growth of streptomycetes coincides with the synthesis and deposition of an uncharacterized protective glucan at hyphal tips. Synthesis of this glucan depends on the integral membrane protein CslA and the radical copper oxidase GlxA, which are part of a presumably large multiprotein complex operating at growing tips. Here, we show that CslA and GlxA interact by forming a protein complex that is sufficient to synthesize cellulose in vitro. Mass spectrometry analysis revealed that the purified complex produces cellulose chains with a degree of polymerization of at least 80 residues. Truncation analyses demonstrated that the removal of a significant extracellular segment of GlxA had no impact on complex formation, but significantly diminished activity of CslA. Altogether, our work demonstrates that CslA and GlxA form the active core of the cellulose synthase complex and provides molecular insights into a unique cellulose biosynthesis system that is conserved in streptomycetes. SignificanceCellulose stands out as the most abundant polysaccharide on Earth. While the synthesis of this polysaccharide has been extensively studied in plants and Gram-negative bacteria, the mechanisms in Gram-positive bacteria have remained largely unknown. Our research unveils a novel cellulose synthase complex formed by the interaction between the cellulose synthase-like protein CslA and the radical copper oxidase GlxA from Streptomyces lividans, a soil-dwelling Gram-positive bacterium. This discovery provides molecular insights into the distinctive cellulose biosynthesis machineries. Beyond expanding our understanding of cellulose biosynthesis, this study also opens avenues for exploring biotechnological applications and ecological roles of cellulose in Gram-positive bacteria, thereby contributing to the broader field of microbial cellulose biosynthesis and biofilm research.

microbiology↗