Primary structure and expression of a gene encoding the cytosolic ribosomal protein S4 from potato

The primary structure of a cDNA clone encoding the S4 protein from the small subunit of 80S ribosomes from potato was determined. Cytosolic ribosomal protein S4 is hydrophilic and has a prevalence for positively charged residues. In potato it is 264 amino acids long and contains a putative nuclear targeting signal close to the N-terminus. Having 65-69% identical amino acids cytosolic ribosomal protein S4 from mammals, fungi and plants belongs to the highly conserved proteins. The S4 gene is transcribed in all potato tissues analysed and has a relatively high expression level in comparison to nuclear genes encoding mitochondrial proteins.