Using LanM Enzymes to Modify Glycagon-Like Peptides 1 and 2 in E.coli.

Selective modification of peptides is often exploited to improve pharmaceutically relevant properties of bioactive peptides like stability, circulation time, and potency. In Nature, natural products belonging to the class of ribosomally synthesized and post-translationally modified peptides (RiPPs) are known to install a number of highly attractive modifications with high selectivity. These modifications are installed by enzymes guided to the peptide by corresponding leader peptides that are removed as the last step of biosynthesis. Here, we exploit leader peptides and their matching enzymes to investigate the installation of D-Ala post-translationally in a critical position in the hormones, glucagon-like peptides (GLP) 1 and 2. We also offer insight into how precursor peptide design can modulate the modification pattern achieved.

Comparison of CRISPR-MAD7 and CRISPR-Cas9 for Gene Disruptions in Komagataella phaffii.

CRISPR (clustered regularly interspaced short palindromic repeats)-based technologies are powerful, programmable tools for site-directed genome modifications. After successful adaptation and efficient use of CRISPR-Cas9 for genome engineering in methylotrophic yeast Komagataella phaffii, a broader variety of employable endonucleases was desired to increase the experimental flexibility and to provide alternatives in case there are specific legal restrictions in industrial research due to the intellectual property rights (IPRs) of third parties. MAD7, an engineered Class 2 Type V Cas nuclease, was promoted as a royalty-free alternative for academic and industrial research and developed by Inscripta (Pleasanton, CA, USA). In this study, for the first time, CRISPR-MAD7 was used for genome editing in K. phaffii with a high gene-editing rate (up to 90%), as demonstrated for the three targeted genes coding for glycerol kinase 1 (GUT1), red fluorescence protein (DsRed), and zeocin resistance gene (Sh ble). Additionally, the genome-editing efficiencies of the CRISPR-MAD7 and CRISPR-Cas9 systems were systematically compared by targeting 259 kinase genes in K. phaffii. In this broad testing, the CRISPR-Cas9 had a higher genome-editing rate of about 65%, in comparison to the applied CRISPR-MAD7 toolbox (about 23%).

Novel Application of Peptidyl-Lys Metallopeptidase as a C-Terminal Processing Protease.

Adding fusion partners to proteins or peptides can aid or be a necessity to facilitate recombinant expression, folding, or purification. Independent of the reason it is desirable to remove the fusion partner to restore native functionality. Processing proteases catalyze the removal of fusion partners, however, most of these proteases have substrate specificity for the N-terminal of the scissile bond, leaving non-native termini if fusions are added to the C-terminal. The peptidyl-lys metallopeptidease of Armillaria mellea (Am-LysN) is unusual by having substrate specificity for the C-terminal side of the scissile peptide bond, allowing it to generate native C-termini. Am-LysN has strict specificity for lysine in P1', making all lysines of a protein or peptide a potential degradation site, however there are a number of amino acid side chains which lower hydrolysis significantly when located adjacent to the lysine. In this study we show that Am-LysN can be used as a processing protease to remove C-terminal extensions of peptides with no internal lysine to generate native Ctermini. Furthermore we show that removal of C-terminal extensions on peptides containing internal lysines can be achieved with little degradation of the product depending on the adjacent amino acids. These results demonstrate the utility of LysN allowing for novel ways to use fusion technology in the production of recombinant proteins.

Heterologous expression of peptidyl-Lys metallopeptidase of Armillaria mellea and mutagenic analysis of the recombinant peptidase.

A method to express, purify and modify the Peptidyl-Lys metallopeptidase (LysN) ofArmillaria melleainPichia pastoriswas developed to enable functional studies of the protease. Based on prior work, we propose a mechanism of action of LysN. Catalytic residues were investigated by site-directed mutagenesis. As anticipated, these mutations resulted in significantly reduced catalytic rates. Additionally, based on molecular modelling eleven mutants were designed to have altered substrate specificity. The S1' binding pocket of LysN is quite narrow and lined with negative charge to specifically accommodate lysine. To allow for arginine specificity in S1', it was proposed to extend the S1' binding pocket by mutagenesis, however the resulting mutant did not show any activity with arginine in P1'. Two mutants, A101D and T105D, showed increased specificity towards arginine in subsites S2'-S4' compared to the wild type protease. We speculate that the increased specificity to result from the additional negative charge which attract and interact with positively charged residues better than the wild type.

Substrate Specificity Profiling of Peptidyl-Lys Metallopeptidase of Armillaria mellea by FRET Based Peptide Library.

Determining the substrate specificity of a protease is essential for developing assays, inhibitors and understanding the mechanisms of the enzyme. In this work, we have profiled the specificity of Peptidyl-Lys metallopeptidase, (LysN), of Armillaria mellea, by a synthetic fluorescence resonance energy transfer (FRET) positional-scanning library. The library was based on a reference sequence K(Abz)-S-A-Q-K-M-V-S-K(Dnp), where the fluorescent donor is 2-aminobenzamide and the quencher is N-2,4-dinitrophenyl. Each position was varied between 19 different amino acids one by one, to reveal the specificity of the protease. LysN exhibits strict specificity for lysine in S1', and has less specificity moving further away from the scissile bond. Additivity between the subsites was observed and the best substrate identified was K(Abz)-M-R-F-K-R-R-R-K(Dnp) with a kcat/KM of 42.6 µM/s. Based on a homology structure model the reference substrate was fitted into the active site using molecular dynamics to propose peptide-enzyme interactions.

Structural and biochemical characterization of the N-terminal domain of flocculin Lg-Flo1p from Saccharomyces pastorianus reveals a unique specificity for phosphorylated mannose.

UNLABELLED: The mechanism of yeast flocculation is generally considered to be mediated through the interaction of cell surface flocculins and mannan carbohydrates. In the present study, the crystal structure of the soluble 25-kDa lectin domain of flocculin 1 from brewer's yeast (Lg-Flo1p) was resolved to 2.5 Å, and its binding specificity towards oligosaccharides was investigated by fluorescence spectroscopy. Lg-Flo1p displays broad specificity towards sugars and has a 14-fold higher affinity for mannose 1-phosphate and glucose 1-phosphate compared to their unphosphorylated counterparts. Based on the results of a structural analysis, we propose that this higher affinity is the result of a charge interaction with a lysine residue in a carbohydrate-binding loop region, NAKAL, unique to NewFlo type flocculins. This raises the possibility of a unique mechanism of flocculation in NewFlo type yeast, which recognizes phosphorylated cell surface mannans. DATABASE: Structural data have been deposited in the Protein Data Bank under accession number 4GQ7.

Further development of the cassette-based pYC plasmid system by incorporation of the dominant hph, nat and AUR1-C gene markers and the lacZ reporter system.

Dominant selection markers encoding hygromycin B phosphotransferase (hph), nourseothricin N-acetyltransferase (nat) and a mutant inositol phosphoceramide synthase (AUR1-C) were all incorporated into the pYC yeast plasmid vector system, thus expanding this system with possible alternatives to the use of G418 resistance. We found the markers to be of use not only in standard laboratory strains of Saccharomyces cerevisiae but also in an industrial strain of S. carlsbergensis (syn. of S. pastorianus) brewing yeast as well as in Saccharomyces kluyveri. As the pYC system contains means of counter-selection for plasmid loss and loop-out of integrated plasmids, it now provides ample opportunities for genetic manipulation of industrial and non-conventional yeasts when the URA3 marker and FOA counter-selection is not an option. Furthermore, the lacZ system for analyzing gene expression was included in the system.

Purification, crystallization and preliminary X-ray diffraction analysis of the carbohydrate-binding domain of flocculin, a cell-adhesion molecule from Saccharomyces carlsbergensis.

The recombinant carbohydrate-binding domain of the cell-surface lectin flocculin from brewer's yeast has been identified, purified and crystallized. The expression of the protein is associated with the nutritional state of the yeast. P2(1)2(1)2(1) crystals with unit-cell parameters a = 36.5, b = 59.7, c = 83.1 A were obtained in hanging drops at 295 K using 25%(w/v) PEG 4000, 0.05 M KH(2)PO(4) as precipitant. X-ray diffraction data have been obtained to 2.6 A. The asymmetric unit contains one molecule and has a solvent content of 32%. An isomorphous PtCl(4)(2-) derivative has been obtained.

The dynamics of the Saccharomyces carlsbergensis brewing yeast transcriptome during a production-scale lager beer fermentation.

The transcriptome of a lager brewing yeast (Saccharomyces carlsbergensis, syn. of S. pastorianus), was analysed at 12 different time points spanning a production-scale lager beer fermentation. Generally, the average expression rapidly increased and had a maximum value on day 2, then decreased as the sugar got consumed. Especially genes involved in protein and lipid biosynthesis or glycolysis were highly expressed during the beginning of the fermentation. Similarities as well as significant differences in expression profiles could be observed when comparing to a previous transcriptome analysis of a laboratory yeast grown in YPD. The regional distribution of various expression levels on the chromosomes appeared to be random or near-random and no reduction in expression near telomeres was observed.