Impact of C-Terminal Chemistry on Self-Assembled Morphology of Guanosine Containing Nucleopeptides.

Herein, we report the design and characterization of guanosine-containing self-assembling nucleopeptides that form nanosheets and nanofibers. Through spectroscopy and microscopy analysis, we propose that the peptide component of the nucleopeptide drives the assembly into β-sheet structures with hydrogen-bonded guanosine forming additional secondary structures cooperatively within the peptide framework. Interestingly, the distinct supramolecular morphologies are driven not by metal cation responsiveness common to guanine-based materials, but by the C-terminal peptide chemistry.

Synthesis and Characterization of 1,2-Dithiolane Modified Self-Assembling Peptides.

This report focuses on the synthesis of an N-terminus 1,2-dithiolane modified self-assembling peptide and the characterization of the resulting self-assembled supramolecular structures. The synthetic route takes advantage of solid-phase peptide synthesis with the on-resin coupling of the dithiolane precursor molecule, 3-(acetylthio)-2-(acetylthiomethyl)propanoic acid, and the microwave-assisted thioacetate deprotection of the peptide N-terminus before final cleavage from the resin to yield the 1,2-dithiolane modified peptide. After the high-performance liquid chromatography (HPLC) purification of the 1,2-dithiolane peptide, derived from the nucleating core of the Aβ peptide associated with Alzheimer's disease, the peptide is shown to self-assemble into cross-β amyloid fibers.

Photocrosslinking of G-Quadruplex-Forming Sequences found in Human Promoters.

While is it well known that human telomeric DNA sequences can adopt G-quadruplex structures, some promoters sequences have also been found to form G-quadruplexes, and over 40% of promoters contain putative G-quadruplex-forming sequences. Because UV light has been shown to crosslink human telomeric G-quadruplexes by cyclobutane pyrimidine dimer (CPD) formation between T's on adjacent loops, UV light might also be able to photocrosslink G-quadruplexes in promoters. To investigate this possibility, 15 potentially UV-crosslinkable G-quadruplex-forming sequences found in a search of human DNA promoters were UVB irradiated in vitro, and three were confirmed to have formed nonadjacent CPDs by mass spectrometry.

Molecular Determinants of Substrate Specificity in Human Insulin-Degrading Enzyme.

Insulin-degrading enzyme (IDE) is a 110 kDa chambered zinc metalloendopeptidase that degrades insulin, amyloid β, and other intermediate-sized aggregation prone peptides that adopt β-structures. Structural studies of IDE in complex with multiple physiological substrates have suggested a role for hydrophobic and aromatic residues of the IDE active site in substrate binding and catalysis. Here, we examine functional requirements for conserved hydrophobic and aromatic IDE active site residues that are positioned within 4.

Evidence for Reverse Hoogsteen Hairpin Intermediates in the Photocrosslinking of Human Telomeric DNA Sequences.

UVB irradiation of human telomeric d(GGGTTA) GGG sequences in potassium ion solution crosslinks the first and third TTA segments through anti cyclobutane pyrimidine dimer (CPD) formation. The photocrosslinking reaction was first proposed to occur through a form 3 two-tetrad G-quadruplex in which the lateral four-nucleotide GTTA loop can interact with an adjacent TTA loop. Curiously, the reaction does not occur with sodium ion, which was explained by the formation of a basket structure which only has three-nucleotide TTA loops that cannot interact.

Functional requirement for human pitrilysin metallopeptidase 1 arginine 183, mutated in amyloidogenic neuropathy.

Here we report the enzymologic characterization of recombinant human pitrilysin metallopeptidase 1 (Pitrm1) and derivative mutants including the arginine-to-glutamine substitution mutant Pitrm1 R183Q, which has been implicated in inherited amyloidogenic neuropathy. Recombinant Pitrm1 R183Q was readily expressed in and purified from Escherichia coli, but was less active than the recombinant wild-type enzyme against recombinant amyloid beta-peptide (Aβ 1-40). A novel fluorogenic substrate derived from the reported Aβ 1-40 core peptide cleavage sequence, Mca-KLVFFAEDK-(Dnp)-OH, was synthesized and applied to real-time kinetic study of Pitrm1 and derivative mutants including Pitrm1 R183Q.