title: Interplay between Structure and Charge as a Key to Allosteric Modulation of Human 20S Proteasome by the Basic Fragment of HIV-1 Tat Protein.
abstract: The proteasome is a giant protease responsible for degradation of the majority of cytosolic proteins. Competitive inhibitors of the proteasome are used against aggressive blood cancers. However, broadening the use of proteasome-targeting drugs requires new mechanistic approaches to the enzyme's inhibition. In our previous studies we described Tat1 peptide, an allosteric inhibitor of the proteasome derived from a fragment of the basic domain of HIV-Tat1 protein. Here, we attempted to dissect the structural determinants of the proteasome inhibition by Tat1. Single- and multiple- alanine walking scans were performed. Tat1 analogs with stabilized beta-turn conformation at positions 4-5 and 8-9, pointed out by the molecular dynamics modeling and the alanine scan, were synthesized. Structure of Tat1 analogs were analyzed by circular dichroism, Fourier transform infrared and nuclear magnetic resonance spectroscopy studies, supplemented by molecular dynamics simulations. Biological activity tests and structural studies revealed that high flexibility and exposed positive charge are hallmarks of Tat1 peptide. Interestingly, stabilization of a beta-turn at the 8-9 position was necessary to significantly improve the inhibitory potency.
authors.affiliation: Department of Biomedical Chemistry, Faculty of Chemistry, University of Gdańsk, Gdańsk, Poland.|Department of Molecular Medicine, Institute of Biotechnology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America.
authors.forename: Przemysław
authors.initials: P
authors.lastname: Karpowicz
authors.affiliation: Department of Molecular Medicine, Institute of Biotechnology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America.
authors.forename: Paweł A
authors.initials: PA
authors.lastname: Osmulski
authors.affiliation: Department of Biomedical Chemistry, Faculty of Chemistry, University of Gdańsk, Gdańsk, Poland.
authors.forename: Julia
authors.initials: J
authors.lastname: Witkowska
authors.affiliation: Department of Organic Chemistry, Faculty of Chemistry, University of Gdańsk, Gdańsk, Poland.
authors.forename: Emilia
authors.initials: E
authors.lastname: Sikorska
authors.affiliation: Department of Biomedical Chemistry, Faculty of Chemistry, University of Gdańsk, Gdańsk, Poland.
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Giżyńska
authors.affiliation: Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Belczyk-Ciesielska
authors.affiliation: Department of Molecular Medicine, Institute of Biotechnology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America.
authors.forename: Maria E
authors.initials: ME
authors.lastname: Gaczynska
authors.affiliation: Department of Biomedical Chemistry, Faculty of Chemistry, University of Gdańsk, Gdańsk, Poland.
authors.forename: Elżbieta
authors.initials: E
authors.lastname: Jankowska
mesh_terms: D000494:Allosteric Regulation; D019943:Amino Acid Substitution; D006801:Humans; D006860:Hydrogen Bonding; D056004:Molecular Dynamics Simulation; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry*; D061988:Proteasome Inhibitors / Q000737:chemistry; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000737:chemistry* / Q000235:genetics
chemical_list: D010446:Peptide Fragments; D061988:Proteasome Inhibitors; D054322:tat Gene Products, Human Immunodeficiency Virus; D046988:Proteasome Endopeptidase Complex