Physicochemical Investigation of Short Homo-Leucinepeptides
Posted: 7 Feb 2020
Date Written: February 6, 2020
Homorepeat regions are attracting considerable attention because of their links to many hereditary and age-related diseases. The homorepeat runs have a strong potential for molecular interaction due to the excessively high local concentration of a certain physicochemical property. The homorepeats look unusually simple compared to typical protein sequences which are characterized by high complexity and absence of strong bias in the amino acid composition. In particular, several poly-Q Containing proteins are associated with inherited neurodegenerative disorders, such as Huntington’s disease, Spinocerebellar ataxia 1,2,3,7 and 17. Despite the widespread presence of asparagine repeats in invertebrate eukaryotes, polyN is curiously quite rare invertebrates. The homorepeat containing proteins of transcription/translation and signalling, account for 24% of enzymes and 12% of adhesion molecules among the protein. The most frequent runs made of large hydrophobic residues contain leucine. A majority of poly-L runs (e.g. 90% in human proteins) occurs within the first 40 amino acid residues of the amino terminus identified as a part of the signal peptide sequence. The growing attention to homo-repeats reflects both the discovery of homorepeat instability and a high capacity for cytotoxicity of these regions.
Here we have undertaken an elaborate biophysical investigation of different lengths of poly leucine peptides of various length (Tripeptide to Decapeptide) using both solid phase and solution phase peptide synthesis. Synthesized peptides were purified and Characterized using RP-HPLC, ESI-MS, FT-IR, CD and Thioflavin T assay. Aggregation kinetics and conformational changes of these polyL peptides of variable length were characterized in vitro using vibrational spectroscopy (ATR-FTIR) under native conditions at very low concentrations. From the various vibrational Amide I, II, III and A bands, the conformations and aggregating natures are identified under various molecular environments. We have also characterized the aggregation morphology of poly-L peptides of varying lengths, under a variety of environments, using SEM and HR-TEM.
Keywords: Homorepeats, Neurodegenarative diseases, polyLeucine
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