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Background: EMILIN-3 is the least characterized member of the EMILIN/Multimerin family. Results: EMILIN-3 forms homotrimers and higher order oligomers, binds heparin, has a dynamic expression during development and a restricted distribution in adult tissues, and serves as a pro-TGF-␤ antagonist. Conclusion:The structure and expression of EMILIN-3 are different from other EMILINs/Multimerins. Significance: EMILIN-3, a TGF-␤ antagonist, is likely to be an important regulator during development of several tissues.

SummaryVon Willebrand factor A (VWA) domains are versatile protein interaction domains with N and C termini in close proximity placing spatial constraints on overall protein structure. The 1.2 Å crystal structures of a collagen VI VWA domain and a disease-causing point mutant show C-terminal extensions that place the N and C termini at opposite ends. This allows a “beads-on-a-string” arrangement of multiple VWA domains as observed for ten N-terminal domains of the collagen VI α3 chain. The extension is linked to the core domain by a salt bridge and two hydrophobic patches. Comparison of the wild-type and a muscular dystrophy-associated mutant structure identifies a potential perturbation of a protein interaction interface and indeed, the secretion of mutant collagen VI tetramers is affected. Homology modeling is used to locate a number of disease-associated mutations and analyze their structural impact, which will allow mechanistic analysis of collagen-VI-associated muscular dystrophy phenotypes.

HighlightsThe expression of matrilin VWA domains was improved.The proper folding was monitored by NMR and CD spectroscopy.Binding properties were analyzed by surface plasmon resonance.Differences between bacterially and eukaryotically expressed domains were detected.We recommend eukaryotic expression for structural analysis.