start-ver=1.4 cd-journal=joma no-vol=7 cd-vols= no-issue=2 article-no= start-page=121 end-page=132 dt-received= dt-revised= dt-accepted= dt-pub-year=2020 dt-pub=20200514 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=The expression level and cytotoxicity of green fluorescent protein are modulated by an additional N-terminal sequence en-subtitle= kn-subtitle= en-abstract= kn-abstract=Nucleotide and amino acid sequences at the N-terminus affect the expression level and cytotoxicity of proteins; however, their effects are not fully understood yet. Here, N-terminal 30 nucleotide/10 amino acid (N10) sequences that affect the expression level and cytotoxicity of a green fluorescent protein were systematically isolated in the budding yeast Saccharomyces cerevisiae. The expression per gene (EPG) and gene copy number limit (CNL) relationships were examined to assess the effects of the N10 sequence. The isolated N10 nucleotide sequences suggested that codon optimality is the major determinant of the protein expression level. A higher number of hydrophobic or cysteine residues in the N10 sequence seemed to increase the cytotoxicity of the protein. Therefore, a high frequency of specific amino acid residues in the outside of the main tertiary structure of proteins might not be preferable. en-copyright= kn-copyright= en-aut-name=MoriyaHisao en-aut-sei=Moriya en-aut-mei=Hisao kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= affil-num=1 en-affil=Graduate School of Environmental and Life Sciences, Research Core for Interdisciplinary Sciences, Okayama University kn-affil= en-keyword=green fluorescent protein kn-keyword=green fluorescent protein en-keyword=overexpression kn-keyword=overexpression en-keyword=expression limit kn-keyword=expression limit en-keyword=expression level kn-keyword=expression level en-keyword=protein cytotoxicity kn-keyword=protein cytotoxicity END