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Chemistry & Biodiversity Feb 2006Catalytic enantioselective methodology has dramatically been enriched by the re-discovery of the simple amino acid proline as a chiral catalyst in the year 2000.... (Review)
Review
Catalytic enantioselective methodology has dramatically been enriched by the re-discovery of the simple amino acid proline as a chiral catalyst in the year 2000. Although no catalyst offers such a simple and broad access to quite complex reaction products, as does proline, its synthetic potential is not unrestricted, what is especially connected to its poor solubility in organic media. Exchange of the carboxylic moiety by a tetrazole unit leads to proline surrogates, that by far outperform proline with respect to yield, enantioselectivity, reaction time, substrate and solvent scope, catalyst loading, and stoichiometry of the compounds used in excess. These factors are discussed and critically compared with selected representative proline-catalyzed reactions.
Topics: Catalysis; Proline; Pyrroles; Pyrrolidines; Stereoisomerism; Tetrazoles
PubMed: 17193251
DOI: 10.1002/cbdv.200690016 -
International Journal of Molecular... Mar 2017Here we discuss studies of the structure, folding, oligomerization and amyloid fibril formation of several proline mutants of human stefin B, which is a protein...
Here we discuss studies of the structure, folding, oligomerization and amyloid fibril formation of several proline mutants of human stefin B, which is a protein inhibitor of lysosomal cysteine cathepsins and a member of the cystatin family. The structurally important prolines in stefin B are responsible for the slow folding phases and facilitate domain swapping (Pro 74) and loop swapping (Pro 79). Moreover, our findings are compared to β₂-microglobulin, a protein involved in dialysis-related amyloidosis. The assessment of the contribution of proline residues to the process of amyloid fibril formation may shed new light on the critical molecular events involved in conformational disorders.
Topics: Amino Acid Sequence; Amyloid; Animals; Cystatin B; Humans; Kinetics; Mice; Models, Molecular; Mutation; Proline; Protein Aggregates; Protein Aggregation, Pathological; Protein Conformation; Protein Folding; Protein Multimerization; Protein Stability; beta 2-Microglobulin
PubMed: 28272335
DOI: 10.3390/ijms18030549 -
Toxicology and Applied Pharmacology Sep 2004The sequence PPGPXPXPXXGN is highly conserved in some cytochromes P450 across species from humans to plants. Within species, however, this specific sequence is not... (Review)
Review
The sequence PPGPXPXPXXGN is highly conserved in some cytochromes P450 across species from humans to plants. Within species, however, this specific sequence is not conserved although a proline-rich sequence is present. In CYP2C proteins, mutagenesis of the prolines and glycine in the PPGPXPXP part of the sequence results in less efficient assembly of native P450 molecules, but those molecules that are formed properly have specific activities similar to wild type suggesting that this region plays a role in folding of the protein. Further, the pattern of requirements for prolines was consistent with a left-handed polyproline II (PPII) helix structure in the PPGP segment. The recent determinations of the structures of CYP2C proteins permit a reinterpretation of these earlier experimental studies. In CYP2C5, the PPGPXPXP part of the sequence is in a left-handed polyproline II-like sequence with a 90 degrees bend at the glycine residue. The PXPXXGN part forms a hairpin structure with the remaining sequence protruding at a right angle. The structure forms tertiary interactions with protein segments centered on Tyr-61, Phe-219, and Tyr-376. van der Waals contacts of the rings of prolines with those of the equally highly conserved tyrosine residues may be particularly important. The proper positioning of the N-terminal segment containing Tyr-61 and the C-terminal segment containing Tyr-376 by interactions with the proline-rich region may be important for proper folding because these residues are in loops extending from four strands of a beta-sheet structure. A schematic model of the sequential folding interactions is presented, and although speculative, it is proposed that constraints required for the folding of a hydrophobic knob that will be inserted into the membrane contribute to the high conservation of the PPGPXPXPXXGN sequence in a subset of cytochromes P450.
Topics: Amino Acid Sequence; Animals; Biological Evolution; Conserved Sequence; Cytochrome P-450 Enzyme System; Humans; Models, Molecular; Molecular Sequence Data; Mutagenesis; Proline; Protein Folding; Species Specificity
PubMed: 15364546
DOI: 10.1016/j.taap.2003.11.030 -
Amino Acids Nov 2008Collagens are among proteins that undergo several post-translational modifications, such as prolyl hydroxylation, that occur during elongation of the nascent chains in... (Review)
Review
Collagens are among proteins that undergo several post-translational modifications, such as prolyl hydroxylation, that occur during elongation of the nascent chains in the endoplasmic reticulum. The major structural collagens, types I, II and III, have large, uninterrupted triple helices, comprising three polyproline II-like chains supercoiled around a common axis. The structure has a requirement for glycine, as every third residue, and is stabilized by the high content of proline and 4-hydroxyproline residues. Action of prolyl hydroxylases is critical. Spontaneous or targeted genetic defects in prolyl hydroxylases can be lethal or result in severe osteogenesis imperfecta. Prolines, as determinants of substrate specificity and susceptibility, also play a role in degradation of collagen by collagenolytic matrix metalloproteinases (MMPs). Targeted mutations in mice in the collagenase cleavage domain have profound effects on collagen turnover and the function of connective tissues. Prolines are thus critical determinants of collagen structure and function.
Topics: Amino Acid Sequence; Animals; Collagen; Glycine; Humans; Hydroxyproline; Mice; Models, Biological; Models, Genetic; Molecular Sequence Data; Mutation; Osteogenesis Imperfecta; Proline; Proteins
PubMed: 18431533
DOI: 10.1007/s00726-008-0073-2 -
The Journal of Biological Chemistry Dec 2020Cellular energy demands are met by uptake and metabolism of nutrients like glucose. The principal transcriptional regulator for adapting glycolytic flux and downstream...
Cellular energy demands are met by uptake and metabolism of nutrients like glucose. The principal transcriptional regulator for adapting glycolytic flux and downstream pathways like lipogenesis to glucose availability in many cell types is carbohydrate response element-binding protein (ChREBP). ChREBP is activated by glucose metabolites and post-translational modifications, inducing nuclear accumulation and regulation of target genes. Here we report that ChREBP is modified by proline hydroxylation at several residues. Proline hydroxylation targets both ectopically expressed ChREBP in cells and endogenous ChREBP in mouse liver. Functionally, we found that specific hydroxylated prolines were dispensable for protein stability but required for the adequate activation of ChREBP upon exposure to high glucose. Accordingly, ChREBP target gene expression was rescued by re-expressing WT but not ChREBP that lacks hydroxylated prolines in ChREBP-deleted hepatocytes. Thus, proline hydroxylation of ChREBP is a novel post-translational modification that may allow for therapeutic interference in metabolic diseases.
Topics: Animals; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; Gene Expression Regulation; Glucose; HEK293 Cells; Humans; Hydroxylation; Liver; Male; Metabolic Diseases; Mice; Mice, Transgenic; Proline; Protein Processing, Post-Translational
PubMed: 33023907
DOI: 10.1074/jbc.RA120.014402 -
Biotechnology Journal Mar 2018Human butyrylcholinesterase (BChE), predominantly tetramers with a residence time of days, offers the potential to scavenge organophosphorus pesticides and chemical...
Human butyrylcholinesterase (BChE), predominantly tetramers with a residence time of days, offers the potential to scavenge organophosphorus pesticides and chemical warfare agents. Efficient assembly of human BChE into tetramers requires an association with proline-rich peptide chaperones. In this study, the incorporation of different proline-rich peptide chaperones into BChE is investigated computationally and experimentally. First, the authors applied molecular dynamic (MD) simulations to interpret the interactions between proline-rich chaperones with human BChE tetramer domains. The P24 chaperone which contains 24 prolines, promoted the association of BChE tetramer with a 74% simulated helicity of BChE subunits, whereas the control without chaperone and BChE with an 8-proline chaperone (P8) complex exhibited 55.8 and 60.6% predicted helicity, respectively. The interaction of proline-rich chaperones with BChE subunits (B-P) provides a conduit to facilitate the interactions between BChE subunits (B-B) of the complex, which is mainly attributed to hydrophobic interactions and hydrogen-bond binding. Experimental assessment of these two proline-rich chaperones plus a 14-proline chaperone (P14) was performed and confirmed that P24 has superior capability to facilitate recombinant BChE (rBChE) tetramerization with >60% rBChE tetramer in P24-transfected rBChE cells, whereas P14- and P8-transfected rBChE cells had 44 and 33% rBChE tetramer, respectively. The rBChE control had 14% tetramer. Finally, we developed a stable rBChE tetramer expression system in CHO cells by enriching P24 expression in rBChE expressing cells. Overall, our simulations provided a design concept for identifying proline-rich peptides that promote the rBChE tetramerization in CHO cells.
Topics: Animals; Butyrylcholinesterase; CHO Cells; Cricetulus; Molecular Chaperones; Proline; Protein Multimerization; Recombinant Proteins
PubMed: 29024569
DOI: 10.1002/biot.201700479 -
Prion 2016Amyloidogenic proteins have an increased propensity to reorganize into the highly structured, β sheet rich structures that characterize amyloid. The probability of...
Amyloidogenic proteins have an increased propensity to reorganize into the highly structured, β sheet rich structures that characterize amyloid. The probability of attaining these highly structured assemblies is influenced by multiple factors, including amino acid composition and environmental conditions. Evolutionary selection for amino acid sequences that prevent amyloid formation could further modulate amyloid-forming propensity. Indeed, we have recently identified specific proline and lysine residues, contained within a highly conserved central region of prion protein (PrP), that impede PrP amyloid formation in vitro. These prolines are mutated in certain forms of the human familial genetic disease, Gerstmann-Straüssler-Schneiker (GSS) syndrome. Here, I discuss the influence of these proline and lysine residues on PrP amyloid formation and how such anti-amyloidogenic primary amino acid sequences might be modulated to influence protein amyloidogenicity.
Topics: Amino Acid Sequence; Amyloid; Humans; Lysine; Mutation; Prion Proteins; Proline
PubMed: 26864641
DOI: 10.1080/19336896.2015.1132138 -
Biophysical Journal Dec 2021The conserved fold of thioredoxin (Trx)-like thiol/disulfide oxidoreductases contains an invariant cis-proline residue (P76 in Escherichia coli Trx) that is essential...
The conserved fold of thioredoxin (Trx)-like thiol/disulfide oxidoreductases contains an invariant cis-proline residue (P76 in Escherichia coli Trx) that is essential for Trx function and that is responsible for the folding rate-limiting step. E. coli Trx contains four additional prolines, which are all in the trans conformation in the native state. Notably, a recent study revealed that replacement of all four trans prolines in Trx by alanines (Trx variant Trx1P) further slowed the rate-limiting step 25-fold, indicating that one or several of the four trans prolines accelerate the trans-to-cis transition of P76 in Trx wild-type (wt). Here, we characterized the folding kinetics of Trx variants containing cisP76 and one or several of the natural trans prolines of Trx wt with NMR spectroscopy. First, we demonstrate that the isomerization reaction in Trx1P is a pure two-state transition between two distinct tertiary structures, in which all observed NMR resonances changes follow the same first-order kinetics. Moreover, we show that trans-P68 is the critical residue responsible for the faster folding of wt Trx relative to the single-proline (P76) variant Trx1P, as the two-proline variant Trx2P(P76P68) already folds seven times faster than Trx1P. trans-P34 also accelerates trans-to-cis isomerization of P76, albeit to a smaller extent. Overall, the results demonstrate that trans prolines can significantly modulate the kinetics of rate-limiting trans-to-cis proline isomerization in protein folding. Finally, we discuss possible mechanisms of acceleration and the potential significance of a protein-internal folding acceleration mechanism for Trx in a living cell.
Topics: Bacterial Outer Membrane Proteins; Escherichia coli; Escherichia coli Proteins; Isomerism; Kinetics; Proline; Protein Conformation; Protein Folding
PubMed: 34736898
DOI: 10.1016/j.bpj.2021.10.040 -
Protein Science : a Publication of the... Apr 2024Evolution leads to conservation of amino acid residues in protein families. Conserved proline residues are usually considered to ensure the correct folding and to...
Evolution leads to conservation of amino acid residues in protein families. Conserved proline residues are usually considered to ensure the correct folding and to stabilize the three-dimensional structure. Surprisingly, proline residues that are highly conserved in class A β-lactamases were found to tolerate various substitutions without large losses in enzyme activity. We investigated the roles of three conserved prolines at positions 107, 226, and 258 in the β-lactamase BlaC from Mycobacterium tuberculosis and found that mutations can lead to dimerization of the enzyme and an overall less stable protein that is prone to aggregate over time. For the variant Pro107Thr, the crystal structure shows dimer formation resembling domain swapping. It is concluded that the proline substitutions loosen the structure, enhancing multimerization. Even though the enzyme does not lose its properties without the conserved proline residues, the prolines ensure the long-term structural integrity of the enzyme.
Topics: Proline; beta-Lactamases; Dimerization; Mycobacterium tuberculosis
PubMed: 38533527
DOI: 10.1002/pro.4972 -
Cell Host & Microbe Mar 2021Most viral vaccines are based on inducing neutralizing antibodies (NAbs) against the virus envelope or spike glycoproteins. Many viral surface proteins exist as trimers... (Review)
Review
Most viral vaccines are based on inducing neutralizing antibodies (NAbs) against the virus envelope or spike glycoproteins. Many viral surface proteins exist as trimers that transition from a pre-fusion state when key NAb epitopes are exposed to a post-fusion form in which the potential for virus-cell fusion no longer exists. For optimal vaccine performance, these viral proteins are often engineered to enhance stability and presentation of these NAb epitopes. The method involves the structure-guided introduction of proline residues at key positions that maintain the trimer in the pre-fusion configuration. We review how this technique emerged during HIV-1 Env vaccine development and its subsequent wider application to other viral vaccines including SARS-CoV-2.
Topics: Antibodies, Neutralizing; COVID-19 Vaccines; Humans; Models, Molecular; Proline; Protein Engineering; Viral Vaccines
PubMed: 33705704
DOI: 10.1016/j.chom.2021.02.002