Recombinant Drosophila melanogaster Glycine-rich selenoprotein (SelG), partial

Introduction to Recombinant Drosophila melanogaster Glycine-Rich Selenoprotein (SelG), Partial

Recombinant Drosophila melanogaster Glycine-rich selenoprotein (SelG), partial, is a selenoprotein identified in the Drosophila melanogaster genome . Selenoproteins incorporate the amino acid selenocysteine, which is specified by the UGA codon that typically acts as a stop signal . SelG lacks sequence similarity to other known proteins and exists as a cysteine homolog in C. elegans .

Identification and Characteristics of dSelG

Computational methods predict selenoproteins in genomic sequences by predicting SECIS elements, which are mRNA structures, in coordination with gene predictions. This involves observing the codon bias extending beyond a TGA codon that interrupts the open reading frame . Using this method, dSelG was identified in Drosophila melanogaster .

Key characteristics of dSelG include:

• It is a novel selenoprotein without significant sequence similarity to known proteins .

• A cysteine homolog exists in C. elegans .

• It is one of three Drosophila melanogaster selenoproteins identified through in silico analysis and confirmed by 75Se labeling .

Selenoproteins and Antioxidant Defense

Selenoproteins have a role in antioxidant defenses in invertebrates . Studies using RNA interference (RNAi) in Drosophila melanogaster embryos and Schneider S2 cells to inhibit the expression of selenoproteins dSelH and dSelK showed that inhibiting either protein significantly reduces viability in embryos . Silencing dSelH decreases total antioxidant capacity and increases lipid peroxidation, while transient expression of dSelH decreases lipid peroxidation and reverses the toxic effects of glutathione depletion, correlating with spared glutathione levels .

Drosophila melanogaster as a Model Organism

Drosophila melanogaster, or the fruit fly, serves as a model for studying complex human biology due to its biological similarity to human systems and genetic tractability . About 75% of human genes associated with diseases have homologs in fruit flies, enabling the study of gene regulation, protein interactions, and post-translational modification of conserved human homologs . Drosophila offers several advantages for studying bacterial interactions, including a simple endogenous microbial community, high-throughput screening potential, genetic tractability, cost-effectiveness, and the ability to recapitulate key virulence events .

Protein Structure Overview

Proteins need to fold into specific spatial conformations to perform their biological functions . There are four levels of protein structure :

1. Primary Structure: The sequence of amino acids in the polypeptide chain, held together by peptide bonds . The primary structure is determined by the gene corresponding to the protein .

2. Secondary Structure: Regular local sub-structures, such as α-helices and β-sheets, defined by hydrogen bonds between main-chain peptide groups .

3. Tertiary Structure: The three-dimensional structure formed by a single protein molecule, including one or more domains . This is stabilized by hydrophobic interactions, salt bridges, hydrogen bonds, and disulfide bonds .

4. Quaternary Structure: The structure formed by multiple protein molecules (polypeptide chains) that operate together as a single functional unit or protein complex .