New 63 knot and other knots in human proteome from AlphaFold predictions

AlphaFold is a new, highly accurate machine learning protein structure prediction method that outperforms other methods. Recently this method was used to predict the structure of 98.5% of human proteins. We analyze here the structure of these AlphaFold-predicted human proteins for the presence of knots. We found that the human proteome contains 65 robustly knotted proteins, including the most complex type of a knot yet reported in proteins. That knot type, denoted 63 in mathematical notation, would necessitate a more complex folding path than any knotted proteins characterized to date. In some cases AlphaFold structure predictions are not highly accurate, which either makes their topology hard to verify or results in topological artifacts. Other structures that we found, which are knotted, potentially knotted, and structures with artifacts (knots) we deposited in a database available at: https://knotprot.cent.uw.edu.pl/alphafold.

Prediction of Human proteins having interactions with HPV16 proteins using virus and host sequence motifs.

Background: Human Papillomavirus (HPV) infection has been found to be the major cause of cancer of cervical region, in females. Genome of HPV codes for 6 functional proteins E1, E2, E4, E5, E6 and E7. These proteins play different roles in development of HPV infection and its progression towards cervical cancer. The interactions of HPV proteins with human DNA and proteins occurs in the presence of short linear peptide motifs on these proteins, have similar sequence to those found on proteins in human cells. Methods: After identification of human motifs in HPV proteins, by use of ELM resource, their counter domains were found from PROSITE. The proteins of human proteome containing these counter domains were predicted as the proteins having possibility of interactions with HPV proteins. Results: we predicted 9468 human proteins for having interactions with HPV proteins. Our predicted proteins were enriched with the host proteins having possibility of being interacted by HPV proteins. 10% of our predicted proteins were already reported to be affected by one or more HPV proteins. The list of predicated proteins can be utilized to find out the connectivity between the virus HPV and human host. It can also be used to determine the pathways involved in pathogenesis of HPV leading towards the cervical cancer Conclusion: The list of predicated proteins can be utilized to find out the connectivity between the virus HPV and human host. It can also be used to determine the pathways involved in pathogenesis of HPV leading towards the cervical cancer.

Embeddings from protein language models predict conservation and variant effects

The emergence of SARS-CoV-2 variants stressed the demand for tools allowing to interpret the effect of single amino acid variants (SAVs) on protein function. While Deep Mutational Scanning (DMS) sets continue to expand our understanding of the mutational landscape of single proteins, the results continue to challenge analyses. Protein Language Models (pLMs) use the latest deep learning (DL) algorithms to leverage growing databases of protein sequences. These methods learn to predict missing or masked amino acids from the context of entire sequence regions. Here, we used pLM representations (embeddings) to predict sequence conservation and SAV effects without multiple sequence alignments (MSAs). Embeddings alone predicted residue conservation almost as accurately from single sequences as ConSeq using MSAs (two-state Matthews Correlation Coefficient—MCC—for ProtT5 embeddings of 0.596 ± 0.006 vs. 0.608 ± 0.006 for ConSeq). Inputting the conservation prediction along with BLOSUM62 substitution scores and pLM mask reconstruction probabilities into a simplistic logistic regression (LR) ensemble for Variant Effect Score Prediction without Alignments (VESPA) predicted SAV effect magnitude without any optimization on DMS data. Comparing predictions for a standard set of 39 DMS experiments to other methods (incl. ESM-1v, DeepSequence, and GEMME) revealed our approach as competitive with the state-of-the-art (SOTA) methods using MSA input. No method outperformed all others, neither consistently nor statistically significantly, independently of the performance measure applied (Spearman and Pearson correlation). Finally, we investigated binary effect predictions on DMS experiments for four human proteins. Overall, embedding-based methods have become competitive with methods relying on MSAs for SAV effect prediction at a fraction of the costs in computing/energy. Our method predicted SAV effects for the entire human proteome (~ 20 k proteins) within 40 min on one Nvidia Quadro RTX 8000. All methods and data sets are freely available for local and online execution through bioembeddings.com, https://github.com/Rostlab/VESPA, and PredictProtein.

GLYCOCONJUGATES IN PROGNOSTIC ANALYSIS AGAINST INFECTIONS AND PATHOGENS: THE KEYS TO APPLICATION

The overview focuses on our own data on the use of water-soluble glycoconjugates (www.lectinity.com) based on a linear polyacrylamide chain in relation to recombinant therapeutic human protein hormones and probiotic recognition proteins such as enzymes and lectins. The results obtained characterize the basic principles of multilevel relationships between proteins and glycoconjugates, including the assembly of complexes and nanoparticles on the solid phase. Prospects for the application of these principles and cases of interaction of proteins and glycoconjugates, including taking into account the participation of enzymes, in the study of human proteins and viruses, are noted. The presented data can help in development of the protective network communication systems as well as new combined preparations against infections and pathogens. These data can serve the keys to be applied in medical biotechnology.

Allergen Shedding in Human Milk from Mothers of Preterm Infants: Proteomic and Peptidomic Feasibility and Pilot Analysis

Rationale: There is little information regarding the allergen content of milk feeds in the preterm population. Previous studies have evaluated specific proteins/peptides via ELISA, but no studies have performed a broad analysis of the allergenic peptide content and protease activity of milk feeds in this population. Preterm infants spend a critical window of time for immune development in the Newborn Intensive Care Unit (NICU), and may receive fortified donor milk, maternal milk or formula feeds via nasogastric tube or bottle instead of fresh breastmilk via breastfeeding. Methods: To evaluate feasibility, we initially performed mass spectrometry on four human milk samples (two term and two preterm) from the Mommy’s Milk Human Milk Biorepository (HMB) which included maternal surveys of diet and environmental exposures. We analyzed the results against the University of Nebraska FASTA database and UniProt for a total of 2211 protein sequences. We then further analyzed 5 samples from the Microbiome, Atopy and Prematurity (MAP) pilot study along with formula and human milk fortifier controls and performed not only mass spectrometry, but also peptidomic and protease activity analysis. Results: Each HMB sample had between 806 and 1007 proteins, with 37 to 44 non-human proteins/sample encompassing 26 plant and animal species. Bovine proteins were the most numerous; seven unique Bos taurus proteins were found in all four samples, and three contained Bos d 5. Cat, dog, mosquito, salmon, and crab were detected in all four samples. All donors ingested fish, shellfish and tree nuts, and all had salmon and crab proteins in their milk samples; two almond proteins were detected in three samples. Aeroallergens, including dust mite (Der f 28, Der f 25) and mold (Cla h 4) were identified in all samples. Two samples contained allergens to latex (Hev b 9) and chicken (Gal d 10). One sample contained several unique proteins, including carrot, two molds (including Pen c 19) and Der f 33-like protein. In the preterm MAP samples, 784 digested non-human proteins were identified, 30 were non-bovine in origin. Proteins from 23 different species including aeroallergens, food, and contact allergens were identified. Protease activity was highest in human milk samples without human milk fortifier and lowest in preterm formula. Conclusions: These findings represent the first preterm milk feed mass spectrometry and protease analysis with identification of known allergenic proteins to food, contact and aeroallergens. The varying degree of protein detection may reflect variable individual secretion and augmentation of feeds. This raises questions of whether the composition of milk feeds in the NICU impact the development of atopic disease in the preterm population and whether the complex interaction between allergens, proteases, and other human milk components can serve to induce sensitization or tolerance to allergens in infants.

Potential coupling between SARS-CoV-2 replicative fitness and interactions of its nucleoprotein with human 14-3-3 proteins

The SARS-CoV-2 nucleocapsid protein (N) is responsible for viral genome packaging and virion assembly. Being highly abundant in the host cell, N interacts with numerous human proteins and undergoes multisite phosphorylation in vivo. When phosphorylated within its Ser/Arg-rich region, a tract highly prone to mutations as exemplified in the Omicron and Delta variants, N recruits human 14-3-3 proteins, potentially hijacking their functions. Here, we show that in addition to phosphorylated Ser197, an alternative, less conserved phosphosite at Thr205 not found in SARS-CoV N binds 14-3-3 with micromolar affinity and is in fact preferred over pS197. Fluorescence anisotropy reveals a distinctive pT205/pS197 binding selectivity towards the seven human 14-3-3 isoforms. Crystal structures explain the structural basis for the discovered selectivity towards SARS-CoV-2 N phosphopeptides, and also enable prediction for how N variants interact with 14-3-3, suggesting a link between the strength of this interaction and replicative fitness of emerging coronavirus variants.

Network analysis of Dengue NS1 interacting core human proteins driving dengue pathogenesis

Aim: We aimed to identify critical human proteins involved in cathepsin L regulation Background: It has been shown that Dengue Virus (DENV) NS1 activates cathepsin L (CTSL). The CTSL activates heparanase, which cleaves heparan sulfate proteoglycans and causes dengue pathogenesis. NS1 directly interacts with PTBP1 and Gab proteins. Gab protein activates the Ras signaling pathway. Still, no known direct interaction partners are linking GAB1 to cathepsin L. Objective: Our objective includes three main points.1-Network analysis of NS1 interacting human proteins 2- Identification of protein-drug and protein-disease interactions 3- Identification of core proteins involved in cathepsin L regulation. Method: We collected NS1 interacting Human proteins from DenHunt, Int-Act Molecular Interaction Database, Virus Mentha, Virus Pathogen Database and Analysis Resource (ViPR), and Virus MINT. We employed Pesca, cytohubba, and centiscape as the significant plug-ins in Cytoscape for network analysis. To study protein-diseases and protein-drugs interaction, we used NetworkAnalyst. Result: Based on the prior knowledge on the interaction of NS1 with GAB1 and PTBP1 human proteins, we found several core proteins that drive dengue pathogenesis. The proteins EED, NXF1, and MOV10, are the mediators between PTBP1 and CTSL. Similarly, DNM2, GRB2, PXN, PTPRC, and NTRK1 mediate GAB1 and PTBP1. The common first neighbors of MOV10, NXF1, and EED were identified, and the common primary pathways in all three subnetworks were mRNA processing and protein translation. The common interaction partners were considered for drug and disease network analysis. These proteins were; PARP1, NFKB2, HDAC2, SLC25A4, ATP5A1, EPN1, CTSL, UBR4, CLK3, and ARPC4. PARP1 was the highly connected node in the protein-drug network. The highest degree protein, LMNA, was associated with many diseases. The NXF1 is connected with LMNA. Here, we reported one essential protein, namely, NXF1 protein, which links PTBP1 with CTSL. The NXF1 is also connected with TPM3, which is connected to CTSL. Conclusion: We listed functionally important proteins which are involved in cathepsin L activation. Based on network properties, we proposed, NXF1 and TPM3 are the important high centrality proteins in dengue infection.

Discovery of lipid-mediated protein-protein interactions in living cells using metabolic labeling with photoactivatable clickable probes

Protein-protein interactions (PPIs) are essential and pervasive regulatory elements in cell biology. Despite development of a range of techniques to probe PPIs in living systems, there is a dearth of approaches to capture interactions driven by specific post-translational modifications (PTMs). Myristoylation is a lipid PTM added to more than 200 human proteins, where it may regulate membrane localization, stability or activity. Here we report design and synthesis of a panel of novel photocrosslinkable and clickable myristic acid analog probes, and their characterization as efficient substrates for human N myristoyltransferases NMT1 and NMT2, both biochemically and through X-ray co-crystallography. We demonstrate metabolic incorporation of probes to label NMT substrates in cell culture and in situ intracellular photoactivation to form a covalent crosslink between modified proteins and their interactors, capturing a snapshot of interactions driven by the presence of the lipid PTM. Proteomic analyses revealed both known and multiple novel interactors of a series of myristoylated proteins, including ferroptosis suppressor protein FSP1 and spliceosome-associated RNA helicase DDX46. The concept exemplified by these probes offers an efficient approach for exploring the PTM-specific interactome, which may prove broadly applicable to other PTMs.

Characterization of the pVHL Interactome in Human Testis Using High-Throughput Library Screening

Functional impairment of the von Hippel-Lindau (pVHL) tumor suppressor is causative of a familiar increased risk to develop cancer. As E3 substrate recognition particle, pVHL marks for degradation the hypoxia inducible factor 1α (HIF-1α) in normoxic conditions, thus acting as a key regulator of both acute and chronic cell adaptation to hypoxia. Further evidence showed pVHL to also play relevant roles in microtubules stabilization, participate in the formation of the extracellular matrix, as well as to regulate cell senescence and apoptosis. Male mice model carrying VHL gene conditional knockout present significative abnormalities in testis development paired with defects in spermatogenesis and infertility, indicating that pVHL exerts testis-specific roles, at least in mice. Here, we describe 55 novel interactors of the human pVHL obtained by testis-tissue library screening. We show that pVHL interacts with multiple human proteins directly involved in spermatogenesis and reproductive metabolism, suggesting that, in addition to its role in cancer formation, pVHL may be pivotal in the correct gonads development also in human.

Homodimeric Minimal Factor H: In Vivo Tracking and Extended Dosing Studies in Factor H Deficient Mice

C3 glomerulopathy (C3G) is associated with dysregulation of the alternative pathway (AP) of complement and treatment options remain inadequate. Factor H (FH) is a potent regulator of the AP. An in-depth analysis of FH-related protein dimerised minimal (mini)-FH constructs has recently been published. This analysis showed that addition of a dimerisation module to mini-FH not only increased serum half-life but also improved complement regulatory function, thus providing a potential treatment option for C3G. Herein, we describe the production of a murine version of homodimeric mini-FH [mHDM-FH (mFH1–5^18–20^R1–2)], developed to reduce the risk of anti-drug antibody formation during long-term experiments in murine models of C3G and other complement-driven pathologies. Our analysis of mHDM-FH indicates that it binds with higher affinity and avidity to WT mC3b when compared to mouse (m)FH (mHDM-FH KD=505 nM; mFH KD=1370 nM) analogous to what we observed with the respective human proteins. The improved binding avidity resulted in enhanced complement regulatory function in haemolytic assays. Extended interval dosing studies in CFH-/- mice (5mg/kg every 72hrs) were partially effective and bio-distribution analysis in CFH-/- mice, through in vivo imaging technologies, demonstrates that mHDM-FH is preferentially deposited and remains fixed in the kidneys (and liver) for up to 4 days. Extended dosing using an AAV- human HDM-FH (hHDM-FH) construct achieved complete normalisation of C3 levels in CFH-/- mice for 3 months and was associated with a significant reduction in glomerular C3 staining. Our data demonstrate the ability of gene therapy delivery of mini-FH constructs to enhance complement regulation in vivo and support the application of this approach as a novel treatment strategy in diseases such as C3G.