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At least 127 records · Page 7Linked to original sources
PubMed1992

Role of proline residues in human lysozyme stability: a scanning calorimetric study combined with X-ray structure analysis of proline mutants.

It has been shown that protein stability can be modulated from site-directed mutations that affect the entropy of protein unfolding [Matthews, B. W., Nicholson, H., & Becktel, W. J. (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 6663-6667]. However, the effect of a specific amino acid replacement on stability highly depends on the location of the mutation site and its environment in the protein structure [Yutani, K., Hayashi, S., Sugisaki, Y., & Ogasahara, K. (1991) Proteins Struct., Funct., Genet. 9, 90-98). To clarify the role of specific proline residues in the thermostability of human lysozyme (h-lysozyme), a series of proline mutants were investigated by means of scanning calorimetry and high-resolution X-ray crystallography. The thermodynamic properties of the mutant and wild-type h-lysozymes are compared and discussed on the basis of their three-dimensional structure. h-Lysozyme contains two proline residues at positions 71 and 103. The Pro71----Gly substitution was found to destabilize h-lysozyme by decreasing the entropic contribution of unfolding by about 2 kcal/mol at 68.8 degrees C. This is consistent with the theoretical expectations for such a substitution. However, the same substitution at position 103 (Pro103----Gly) does not affect h-lysozyme stability, and the thermodynamic properties of the P71G/P103G and P71G mutants are essentially the same. Pro71 which is conserved among lysozymes from other species, appears to be important for stability, whereas Pro103, which is not conserved, does not. These differences are explained in terms of residue accessibility to the solvent and crystallographic B-factor, which reflects the amino acid mobility.(ABSTRACT TRUNCATED AT 250 WORDS)

Calorimetry, Differential Scanning↗
PubMed2004

A likely biogenetic gateway linking 2-aminoimidazolinone metabolites of sponges to proline: spontaneous oxidative conversion of the pyrrole-proline-guanidine pseudo-peptide to dispacamide A.

A new spontaneous oxidative transformation of the associated pyrrole-proline-guanidine to the natural marine pyrrole 2-aminoimidazolinone derivative has been achieved. The sensitive reaction requires air oxygen and the N-acylation of proline by pyrrole-2-carboxylic acid. Proline metabolism and pyrrole 2-aminoimidazole secondary metabolites formation seem to be related and are utilized by sponges under stress conditions for their defense against predators. A plausible stress-induced oxidative chemical pathway that establishes dispacamide derivatives as the forerunners in the biogenetic synthesis of the key pyrrole 2-aminoimidazole oroidin is proposed. The mechanism of the reaction seems to be another development of the known luciferins' chemiluminescent reactions in bioluminescent marine organisms.

Amination↗
PubMed1999

A novel NMR experiment for the sequential assignment of proline residues and proline stretches in 13C/15N-labeled proteins.

A new pulse sequence is described for the sequential assignment of proline residues in 13C/15N-labeled proteins by correlating C delta and C alpha chemical shifts of proline residues with the H alpha chemical shift of the preceding residue. Notably, the experiment can provide the sequential connectivities in poly-proline stretches, which cannot be determined using standard triple resonance experiments. Excellent solvent suppression is achieved by coherence selection via a heteronuclear gradient echo. The new pulse sequence has been successfully applied to the 11 kDa HRDC domain.

Amino Acid Sequence↗
PubMed1995

Novel 2- and 5-azido-N-(diphenylcarbamoyl)proline methyl esters. Examples of a novel proline oxidation.

The crystal structures of two azido-substituted proline derivatives are reported. Racemic 2-azido-1-(diphenyl-carbamoyl)proline methyl ester, (I), C19H19N5O3, is resolved upon crystallization from methylene chloride-diethyl ether. The azido moieties are nonlinear with N--N--N angles of 173 (1) and 170.3 (2) degrees for (I) and (II) [cis-5-azido-N-(diphenylcarbamoyl)proline methyl ester, C19H19N5O3], respectively. Close intramolecular contacts between the carbonyl O atom of the amide and the central N atom of the azido group are found. The contact distances between N7 and O14 are 2.780 (14) and 2.815 (2) A for (I) and (II), respectively.

Crystallography, X-Ray↗
PubMed1999

Bioactivity of peptide analogs of the neutrophil chemoattractant, N-acetyl-proline-glycine-proline.

PURPOSE: The release of N-acetyl-proline-glycine-proline (PGP), a chemoattractant resulting from direct alkaline hydrolysis of corneal proteins, is believed to be the initial trigger for neutrophil invasion into the alkali-injured cornea. The purpose of this study is twofold: (1) to compare the activity of N-acetyl-PGP with the bioactivities of other similar synthetic peptides in an effort to uncover information about this chemoattractant molecule, and (2) to test these peptide analogs as potential antagonists of N-acetyl-PGP. METHODS: The polarization assay was used to measure the potential chemotactic response of human neutrophils to peptides. Bioactivity was expressed as the peptide concentration required to produce 50% neutrophil polarization (EC50). Antagonist activity was expressed as the peptide concentration required to produce 50% inhibition (ID50) of polarization activated by N-acetyl-PGP. RESULTS: Peptide bioactivities (EC50) were ranked as follows: APGPR (0.34 mM) > N-acetyl-PGP (0.5 mM) > N-(PGP)4-PGLG (3 mM) = t-Boc-PGP (3 mM) > N-acetyl-PG (3.4 mM) > N-methyl-PGP (15 mM) = PGP (15 mM) > peptides without detectable activity (t-Boc-PGP-OMe, N-acetyl-P, PG, PGG, GP, GG and gly-pro-hyp). Peptides with no detectable bioactivity were tested as potential antagonists of neutrophil polarization induced by N-acetyl-PGP. Gly-Pro-Hyp inhibited N-acetyl-PGP activation of polarization at 20 mM (ID50). No other synthetic peptide demonstrated a capacity for inhibition. CONCLUSIONS: The minimum requirement to elicit bioactivity was the presence of PGP alone or derivatives of PG in which the N-terminal proline is blocked. Using this approach, active and inactive mimetic peptides of N-acetyl-PGP were produced. The most active peptide, APGPR, was equal to or slightly greater than N-acetyl-PGP, suggesting that more potent analogs might be designed. Gly-pro-hyp was the only inactive peptide analog to inhibit the chemoattractant.

Chemotactic Factors↗
PubMed1984

Nucleotide sequence analysis of a proline-rich protein cDNA and peptide homologies of rat and human proline-rich proteins.

Plasmids containing cDNAs for proline-rich proteins have been isolated from a cDNA library prepared from parotid glands of isoproterenol-treated rats. The nucleotide sequence of one of these cDNAs (pRP33) has been determined, and it encodes an acidic proline-rich protein. The N-terminal 13 amino acids are highly hydrophobic and may be part of a signal peptide. The next 66 amino acids constitute an acidic domain which is interrupted by a short (8 residue) basic region. The sequence beginning at proline 80 contains six tandemly repeated regions of 18 to 19 amino acids in length with the prototype sequence PPPQGGPQXPPQPGXPQG. Two pairs of these repeats (amino acid residues 116 to 152 and 153 to 189) are 93% homologous in nucleotide sequence. The high homology in both nucleotide and amino acid sequences in the repeat region suggests that this protein may have evolved by duplication of internal portions of a progenitor gene.

Amino Acid Sequence↗
PubMed1983

Proline-rich polypeptides bound to rat prostatic binding protein. The primary structure of the two main components, proline-rich polypeptides IV and V.

The complete primary structures of the two main forms, PRP-IV and PRP-V, of a proline-rich polypeptide bound in vivo to rat prostatic binding protein has been determined. Their sequences were established using manual Edman degradation of the native polypeptide and of purified fragments derived from trypsin and thermolysin digestions. Both polypeptides contain 38 amino acid residues (Mr = 4397 and 4339); cysteine, methionine, and serine are missing. In spite of the high proline content (21%), no polyproline stretches were detected. PRP-IV and PRP-V show an extensive structural homology and differ only by three substitutions. These amino acid replacements are located in the NH2-terminal part of the molecule at positions 6 (His leads to Pro), 10 (Pro leads to His), and 11 (Asp leads to Gly). Moreover, each component displays a microheterogeneity at several positions in the sequence which indicates that multiple structural variants exist for PRP-IV and PRP-V. These data not only suggest the existence in rat ventral prostate of a multigene family coding for the proline-rich polypeptides but also the occurrence of a pronounced genetic polymorphism for these components. In addition, a remarkable sequence homology is observed between the PRP components and the region of the B chain in the precursor of mouse renin.

Amino Acid Sequence↗
PubMed1987

4-Proline and 4-hydroxyproline analogs of arginine vasopressin: role of the proline substitution in the two beta-turns of vasopressin.

[4-L-Proline]arginine vasopressin, [4-D-proline]arginine vasopressin, [4-hydroxyproline]arginine vasopressin and [4-proline, 7-hydroxyproline] arginine vasopressin were synthesized and found to have antidiuretic activities of 91 +/- 4, 1.7 +/- 0.2, 1.0 +/- 0.1 and 4.4 +/- 1.0 units/mg, respectively. None of these analogs exhibited a significant level of rat pressor activity. The observed activities of these and other analogs with substitutions at position 4 and/or 7 are discussed on the basis of hypotheses and data bearing on the solution conformation of vasopressins.

Animals↗
PubMed1988

[Synthesis of N-alpha-(arylsulfonyl)-4-amidino-phenylalanyl-prolines and N-alpha-(arylsulfonylglycyl)-4-amidino-phenylalanyl-prolines and testing of them as inhibitors of serine proteinases. 33. Synthetic inhibitors of serine proteinases].

The headline compounds were prepared by the reaction of N alpha-(arylsulfonyl)- and N alpha-(arylsulfonylglycyl)-4-cyanophenylalanines to the L- and D-proline derivatives. These compounds were transformed in a usual manner in the amidino compounds. The substitution of the pyrrolidine residue by L-proline in this type of inhibitors decreased the activity against serine proteases, especially against thrombin. In the case of the D-proline derivatives the decrease of the inhibitor activity against thrombin was very high.

Chemical Phenomena↗
PubMed1996

Tannin interactions with a full-length human salivary proline-rich protein display a stronger affinity than with single proline-rich repeats.

The protein IB5 has been purified from human parotid saliva. This protein contains several repeats of a short proline-rich sequence. Dissociation constants have been measured at several discrete binding sites using 1H-NMR for the hydrolysable tannins (polyphenols) beta-1,3,6-tri-O-galloyl-D-glucopyranose, beta-1,2,4,6-tetra-O-galloyl-D-glucopyranose and beta-1,2,3,4,6-penta-O-galloyl-D-glucopyranose and the condensed proanthocyanidin (--)-epicatechin. The dissociation constants for trigalloyl glucose and pentagalloyl glucose were 15 X 10(-5) and 1.7 X 10(-5) M, respectively, which are 115 and 1660 times stronger than those previously measured under the same conditions for a single repeat of a mouse salivary proline-rich protein. The increase in affinity is ascribed to intramolecular secondary interactions, which are strengthened by the rigidity of the interacting molecules.

Amino Acid Sequence↗
PubMed1980

The amino acid sequence of a salivary proline-rich peptide, P-C, and its relation to a salivary proline-rich phosphoprotein, protein C.

A basic proline-rich peptide, P-C, was isolated from human whole saliva and its amino acid sequence was determined to be Gly-Arg-Pro-Gln-Gly-Pro-Pro-Gln-Gln-Gly-Gly-His-Gln-Gln-Gly-Pro-Pro-Pro-Pro-Pro-Pro-Gly-Lys-Pro-Gln-Gly-Pro-Pro-Pro-Gln-Gly-Gly-Arg-Pro-Gln-Gly-Pro-Pro-Gln-Gly-Gln-Ser-Pro-Gln. P-C was also found to be present in stimulated parotid saliva. The sequence determined appears to correspond to the C-terminal 44 residues of a proline-rich phosphoprotein, Protein C, the partial sequence of which has been elucidated, and suggests that P-C might be derived from Protein C.

Adult↗
PubMed2005

Probing the "additive effect" in the proline and proline hydroxamic acid catalyzed asymmetric addition of nitroalkanes to cyclic enones.

The effect of chirality and steric bulk of 2,5-disubstituted piperazines as additives in the conjugate addition of 2-nitropropane to cyclohexenone, catalyzed by l-proline, was investigated. Neither chirality nor steric bulk affects the enantioselectivity of addition, which gives 86-93% ee in the presence of achiral and chiral nonracemic 2,5-disubstituted piperazines. Proline hydroxamic acid is shown for the first time to be an effective organocatalyst in the same Michael reaction.

Alkanes↗
PubMed2005

Capillary array electrophoresis for the research of asymmetric transformation reaction of L-proline to D-proline.

One asymmetric transformation reaction of L-proline (L-Pro) to D-proline was studied by a home-made capillary array electrophoresis (CAE) for the first time. The aldehyde catalysts and the organic acid solvents for the asymmetric transformation reaction were rapidly screened and the enantiomeric excess values of the asymmetric product of L-Pro were directly obtained from the electrophoretogram of CAE.

Aldehydes↗
PubMed1990

The Na(+)-dependent proline carrier, of eel intestinal brush-border membrane, sequentially binds proline and then Na+.

The mechanism of Na+/L-proline cotransport, present on brush-border membrane (BBM) vesicles of the European eel intestine, was studied. Initial cotransport rates, depending on increasing proline and Na+ concentrations in the extravesicular medium (zero-trans conditions), were measured by monitoring the decay of an inside-negative membrane potential, i.e. the fluorescence quenching of the voltage-sensitive cyanine dye 3,3'-diethylthiacarbocyanine iodide (DiS-C2(5)). By simultaneously estimating the substrate-dependent Na(+)-influx (with the fluorescent dye) and the Na(+)-dependent [3H]substrate influx, it was concluded that proline was cotransported with 1 Na+ ion and glucose with 2 Na+ ions. The kinetics of proline/Na+ cotransport were then investigated. Graphical analysis excluded a ping-pong mechanism. Under rapid equilibrium assumptions, by fitting model equations to rate values it was possible to exclude the random and the ordered Na+/proline mechanisms. Therefore, in eel intestinal BBM vesicles, the mechanism of proline/Na+ cotransport is ordered and prolineout binds to the carrier prior to Na+out.

Amino Acid Transport Systems, Neutral↗
PubMed2006

Structure-activity relationship study between Ornithyl-Proline and Lysyl-Proline based tripeptidomimics as angiotensin-converting enzyme inhibitors.

A designed library of tripeptidomimics of Ornithyl-Proline (Orn-Pro) and Lysyl-Proline (Lys-Pro) conjugated with various unnatural amino acids and carboxylic acid derived heterocyclics was synthesized and screened for possible inhibitors of angiotensin-converting enzyme (ACE). Among the tripeptidomimics 10[MTP-Orn-Pro], 11[HTP-Orn-Pro], 14[TA-Orn-Pro] and 20[BPA-Orn-Pro] showed prominent inhibition with IC50 values in micromolar concentrations. Structure-activity relationship study indicated that C3 side chain of Orn as compared to C4 side chain of Lys at P1' position was better suited to inhibit ACE, with propionic acid (C3) derived heterocyclics and unnatural amino acids.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2006

Oligomerisation of the developmental regulator proline rich homeodomain (PRH/Hex) is mediated by a novel proline-rich dimerisation domain.

Homeodomain proteins regulate multiple developmental pathways by altering gene expression temporally and in a tissue-specific fashion. The Proline Rich Homeodomain protein (PRH/Hex) is a transcription factor and an essential regulator of embryonic development and haematopoiesis. Recent discoveries have implicated self-association as an important feature of transcription factor function. Here, we show using a variety of techniques including gel-filtration, analytical ultracentrifugation, electron microscopy and in vitro cross-linking, that purified recombinant PRH is oligomeric and we use in vivo cross-linking to confirm that this protein exists as oligomers in cells. This is the first demonstration that a homeodomain protein can oligomerise in vivo. Consistent with these findings we show that a fraction of endogenous and exogenous PRH appears as discrete foci within the nucleus and at the nuclear periphery. The N-terminal domain of PRH is involved in the regulation of cell proliferation and transcriptional repression and can make multiple protein-protein interactions. We show that this region of PRH contains a novel proline-rich dimerisation domain that mediates oligomerisation. We propose a model that explains how PRH forms oligomers and we discuss how these oligomers might control transcription.

Amino Acid Sequence↗
PubMed2003

Kinetic and stereochemical evidence for the involvement of only one proline molecule in the transition states of proline-catalyzed intra- and intermolecular aldol reactions.

Contrary to the widely accepted mechanism of the Hajos-Parrish-Eder-Sauer-Wiechert reaction, we have obtained evidence for the involvement of only one proline molecule in the transition states of both inter- and intramolecular aldol reactions. Our conclusions are based on kinetic measurements and the absence of nonlinear and dilution effects on the asymmetric catalysis, and are supported by B3LYP/6-31G* calculations. Complementary to recent theoretical studies, our results provide the foundation of a unified enamine catalysis mechanism of proline-catalyzed inter- and intramolecular aldol reactions.

Alcohols↗