Background:The sulfur carrier protein TusA is involved in sulfur transfer to different biomolecules in the cell. Results: TusA is involved in sulfur transfer for molybdopterin. Conclusion: Direction of sulfur transfer to biomolecules is mediated by the interaction partners of IscS. Significance: This study furthers the understanding of how sulfur transfer is regulated in bacteria.

Background: Localization and identification of interaction partners of two splice variants of the human 3-mercaptopyruvate sulfurtransferase TUM1. Results: We show that TUM1 interacts with proteins involved in Moco and FeS cluster biosynthesis. Conclusion: Human TUM1 is a dual localized protein in the cytosol and mitochondria with distinct roles in sulfur transfer and interaction partners. Significance: The study contributes to the sulfur transfer pathway for the biosynthesis of sulfur-containing biofactors.

Metal-containing formate dehydrogenases (FDH) catalyse the reversible oxidation of formate to carbon dioxide at their molybdenum or tungsten active site. They display a diverse subunit and cofactor composition, but structural information on these enzymes is limited. Here we report the cryo-electron microscopic structures of the soluble Rhodobacter capsulatus FDH (RcFDH) as isolated and in the presence of reduced nicotinamide adenine dinucleotide (NADH). RcFDH assembles into a 360 kDa dimer of heterotetramers revealing a putative interconnection of electron pathway chains. In the presence of NADH, the RcFDH structure shows charging of cofactors, indicative of an increased electron load.

Trimeric photosystem I from the cyanobacterium Thermosynechococcus elongatus ( Te PSI) is an intrinsic membrane protein, which converts solar energy into electrical energy by oxidizing the soluble redox mediator cytochrome c 6 (Cyt c 6 ) and reducing ferredoxin. Here, we use cryo-electron microscopy and small angle neutron scattering (SANS) to characterize the transient binding of Cyt c 6 to Te PSI. The structure of Te PSI cross-linked to Cyt c 6 was solved at a resolution of 2.9 Å and shows additional cofactors as well as side chain density for 84% of the peptide chain of subunit PsaK, revealing a hydrophobic, membrane intrinsic loop that enables binding of associated proteins. Due to the poor binding specificity, Cyt c 6 could not be localized with certainty in our cryo-EM analysis. SANS measurements confirm that Cyt c 6 does not bind to Te PSI at protein concentrations comparable to those for cross-linking. However, SANS data indicate a complex formation between Te PSI and the non-native mitochondrial cytochrome from horse heart (Cyt c HH ). Our study pinpoints the difficulty of identifying very small binding partners (less than 5% of the overall size) in EM structures when binding affinities are poor. We relate our results to well resolved co-structures with known binding affinities and recommend confirmatory methods for complexes with K M values higher than 20 μM.

Polymeric antimicrobial peptide mimics are a promising alternative for the future management of the daunting problems associated with antimicrobial resistance. However, the development of successful antimicrobial polymers (APs) requires careful control of factors such as amphiphilic balance, molecular weight, dispersity, sequence, and architecture. While most of the earlier developed APs focus on random linear copolymers, the development of APs with advanced architectures proves to be more potent. It is recently developed multivalent bottlebrush APs with improved antibacterial and hemocompatibility profiles, outperforming their linear counterparts. Understanding the rationale behind the outstanding biological activity of these newly developed antimicrobials is vital to further improving their performance. This work investigates the physicochemical properties governing the differences in activity between linear and bottlebrush architectures using various spectroscopic and microscopic techniques. Linear copolymers are more solvated, thermo-responsive, and possess facial amphiphilicity resulting in random aggregations when interacting with liposomes mimicking Escheria coli membranes. The bottlebrush copolymers adopt a more stable secondary conformation in aqueous solution in comparison to linear copolymers, conferring rapid and more specific binding mechanism to membranes. The advantageous physicochemical properties of the bottlebrush topology seem to be a determinant factor in the activity of these promising APs.

Polymeric antimicrobial peptide mimics are a promising alternative for the future management of the daunting problems associated with antimicrobial resistance. However, the development of successful antimicrobial polymers (APs) requires careful control of factors such as amphiphilic balance, molecular weight, dispersity, sequence, and architecture. While most of the earlier developed APs focused on random linear copolymers, the development of APs with advanced architectures proved to be more potent in the mimicry of antimicrobial peptides. We recently developed multivalent bottlebrush APs with improved antibacterial and hemocompatibility profiles, outperforming their linear counterparts. Understanding the rationale behind the outstanding biological activity of these newly developed antimicrobials is vital to further improving their performance. This work investigates the physicochemical properties governing the differences in activity between linear and bottlebrush architectures using diverse spectroscopic and microscopic techniques. Linear copolymers are more solvated, thermo-responsive and possess facial amphiphilicity resulting in random aggregations when interacting with liposomes mimicking E. coli-membranes. The bottlebrush copolymers adopt a more stable secondary conformation in aqueous solution in comparison to linear copolymers, conferring rapid and more specific binding mechanism to membranes. The advantageous physicochemical properties of the bottlebrush topology seem to be a determinant factor in the activity of these promising APs.

No abstract

The conserved TREX complex has multiple functions in gene expression such as transcription elongation, 3′ end processing, mRNP assembly and nuclear mRNA export as well as the maintenance of genomic stability. In S. cerevisiae, TREX is composed of the pentameric THO complex, the DEAD-box RNA helicase Sub2, the nuclear mRNA export adaptor Yra1 and the SR-like proteins Gbp2 and Hrb1. Here, we present the structural analysis of the endogenous TREX complex of S. cerevisiae purified from its native environment. To this end, we used cross-linking mass spectrometry to gain structural information on regions of the complex that are not accessible to classical structural biology techniques. We also used negative-stain electron microscopy to investigate the organization of the cross-linked complex used for XL-MS by comparing our endogenous TREX complex with recently published structural models of recombinant THO-Sub2 complexes. According to our analysis, the endogenous yeast TREX complex preferentially assembles into a dimer. The overall structures of the recombinant yeast THO-Sub2 complexes strongly resemble the structural conformation of the monomers and the dimer interface of the endogenous TREX complex.