Project description:we wanted to see where and how the protein p37 interacts with its partner proteins p97, PPI,Sds22 and I3. To this end p37 derivatives with genetically encoded crosslinking amino acid (p-benzoyl-L-phenylalanine) were generated. After incubation with the partner proteins, photocross-linking and tryptic digest the resulting cross-linked peptides were analysed by mass spectrometry.
Project description:We wanted to see where and how the protein p97 interacts with its partner proteins p37, PPI,Sds22 and I3. To this end a p97 derivative with genetically encoded crosslinking amino acid (p-benzoyl-L-phenylalanine) was generated. After incubation with the partner proteins, photocross-linking and tryptic digest the resulting cross-linked peptides were analysed by mass spectrometry.
Project description:ATP-sensitive potassium (K-ATP) channels composed of a pore-forming Kir6.2 potassium channel and a regulatory ABC transporter sulfonylurea receptor 1 (SUR1) regulate insulin secretion in pancreatic beta-cells to maintain glucose homeostasis. Mutations that impair channel folding or assembly prevent cell surface expression and cause congenital hyperinsulinism. Structurally diverse K-ATP inhibitors have been shown to act as pharmacochaperones to correct mutant channel expression, but the mechanism is unknown. Here, we compare cryoEM structures of K-ATP channels bound to pharmacochaperones glibenclamide, repaglinide, and carbamazepine. CyanurBiotinDimercaptoPropionylSuccinimide (CBDPS) cross-linking mass spectrometry was used to partially confirm cryoEM structures.
Project description:Chromatin remodelers are ATP-dependent enzymes that reorganize nucleosomes within all eukaryotic genomes. The Chd1 remodeler specializes in shifting nucleosomes into evenly spaced arrays, a defining characteristic of chromatin in gene bodies that blocks spurious transcription initiation. Linked to some forms of autism and commonly mutated in prostate cancer, Chd1 is essential for maintaining pluripotency in stem cells. Here we report a complex of yeast Chd1 bound to a nucleosome in a nucleotide-free state, determined by cryo-electron microscopy (cryo-EM) to 2.6 Å resolution. The structure shows a bulge of the DNA tracking strand where the ATPase motor engages the nucleosome, consistent with an initial stage in DNA translocation. Unlike other remodeler-nucleosome complexes, nucleosomal DNA compensates for the remodeler-induced bulge with a bulge of the complementary DNA strand one helical turn downstream from the ATPase motor. Unexpectedly, the structure also reveals an N-terminal binding motif, called ChEx, which binds on the exit-side acidic patch of the nucleosome. The ChEx motif can displace a LANA-based peptide from the acidic patch, which suggests a means by which Chd1 remodelers may block competing chromatin remodelers from acting on the opposite side of the nucleosome.
Project description:The hexameric AAA+ ATPase p97/VCP functions as an essential mediator of ubiquitin-dependent cellular processes, extracting ubiquitylated proteins from macromolecular complexes or membranes by catalyzing their unfolding. p97 is directed to ubiquitylated client proteins via multiple cofactors, most of which interact with the p97 N-domain. Here, we discover that FAM104A, a protein of unknown function also named VCF1 (VCP/p97 nuclear Cofactor Family member 1), acts as a novel p97 cofactor in human cells. Detailed structure-function studies reveal that VCF1 directly binds p97 via a conserved novel -helical motif that recognizes the p97 N-domain with unusually high affinity, exceeding that of other cofactors. We show that VCF1 engages in joint p97 complex formation with the heterodimeric primary p97 cofactor UFD1-NPL4 and promotes p97-UFD1-NPL4-dependent proteasomal degradation of ubiquitylated substrates in cells. Mechanistically, VCF1 indirectly stimulates UFD1-NPL4 interactions with ubiquitin conjugates via its binding to p97 but has no intrinsic affinity for ubiquitin. Collectively, our findings establish VCF1 as an unconventional p97 cofactor that promotes p97-dependent protein turnover by facilitating p97-UFD1-NPL4 recruitment to ubiquitylated targets.
Project description:Here we present data using chemical crosslinking to inform on the architecture of the SPATA5-SPATA5L1-C1orf109-CINP complex (or the 55LCC).
Project description:To investigate the structural basis of SurA’s chaperone function, we characterized crosslinks between it and two of its clients, OmpA and OmpX, and used those as distance restraints to build structural models.
Project description:Adenovirus (AdV) infection of the respiratory epithelium is common but poorly understood. Human infective species C AdVs, such as HAdV-C5, utilise the Coxsackie-Adenovirus receptor (CAR) for attachment and subsequently integrins for entry. CAR and integrins are however located deep within the tight junctions in the mucosa where they would not be easily accessible. Recently, a model for CAR-independent AdV entry was proposed. In this model, Lactoferrin (LF), an innate immune protein, aids the viral uptake into epithelial cells by mediating interactions between the major capsid protein, hexon, and yet unknown host cellular receptor(s). Yet, a detailed understanding of the molecular interactions driving this mechanism is lacking. Here, we present a novel cryo-EM structure of HAd-5C hexon at high resolution alongside a hybrid structure of human lactoferrin (hLF) complexed with HAdV-5C hexon. These structures reveal the molecular determinants of the interaction between hLF and HAdV-C5 hexon. hLF engages hexon primarily via its N-terminal Lactoferricin (Lfcin) region, interacting with hexon's hypervariable region 1 (HVR-1). Mutational analyses pinpoint critical Lfcin contacts but also identify additional regions within hLF that critically contribute to hexon binding. Our study sheds more light on the intricate mechanism by which HAdV-C5 utilises soluble hLF/Lfcin for cellular entry. These findings hold promise for advancing gene therapy applications and inform vaccine development.
Project description:Here we made an attempt to obtain partial structural information on the topology of multispan integral membrane proteins of yeast by isolating organellar membranes, removing peripheral membrane proteins at pH 11.5 and introducing chemical crosslinks between vicinal amino acids either using homo- or hetero-bifunctional crosslinkers. Proteins were digested with specific proteases and the products analysed by mass spectrometry. Dedicated software tools were used together with filtering steps optimized to remove false positive crosslinks. In proteins of known structure, crosslinks were found only between loops residing on the same side of the membrane. As may be expected, crosslinks were mainly found in very abundant proteins. Our approach seems to hold to promise to yield low resolution topological information for naturally very abundant or strongly overexpressed proteins with relatively little effort.