Hydrophobic core formation in protein complex of cathepsin

Genetic traces of never born proteins

The presented results cover issues related to proteins that were “never born in nature”. The paper is focused on identifying genetic information stretches of protein sequences that were not identified to be existing in nature. The aim of the work was finding traces of “never born proteins” (NBP) everywhere in completely sequenced genomes including regions not expected as carrying the genetic information. The results of analyses relate to the search of the genetic material of species from different levels of the evolutionary tree from yeast through plant organisms up to the human genome. The analysis concerns searching the genome sequences. There are presented statistical details such as sequence frequencies, their length, percent identity and similarity of alignments, as well as E value of sequences found. Computations were performed on gLite-based grid environment. The results of the analyses showed that the NBP genetic record in the genomes of the studied organisms is absent at a significant level in terms of identity of contents and length of the sequences found. Most of the found sequences considered to be similar do not exceed 50% of the length of the NBP output sequences, which confirms that the genetic record of proteins is not accidental in terms of composition of gene sequences but also as regards the place of recording in genomes of living organisms.

Structural role of exon-coded fragment of polypeptide chains in selected enzymes

This paper discusses the structural role of fragments encoded by individual exons in proteins. Selected enzymes (hydrolases, transferases, ligases) reveal the presence of at least one exon fragment whose contribution to the protein's hydrophobic core is in line with theoretical expectations. This phenomenon is confirmed by quantitative analysis of the hydrophobicity density distribution in protein molecules. Results are compared with a 3D Gaussian function, treated as an "idealized" distribution of hydrophobicity density, with the highest values observed near the center of the molecule and near-zero values on its surface. At least one accordant exon fragment has been identified in each of the proteins subjected to analysis. On the basis of these results the authors propose that accordant exons are responsible for tertiary structural stabilization of proteins by ensuring the generation of a stable hydrophobic core.