Abstract: The present invention provides a simple and inexpensive system for regulating signal peptide performance by using a synthetically evolved nucleotide sequence. The invention further relates to an expression vector comprising the nucleotide sequence. Additionally, the present invention relates to host cell comprising the expression vector. Furthermore, the present invention relates to a recombinant protein expressed by the host cell as well as a method for expressing the recombinant protein.

Abstract: The present invention provides a simple and inexpensive system for regulating signal peptide performance by using a synthetically evolved nucleotide sequence. The invention further relates to an expression vector comprising the nucleotide sequence. Additionally, the present invention relates to host cell comprising the expression vector. Furthermore, the present invention relates to a recombinant protein expressed by the host cell as well as a method for expressing the recombinant protein.

Abstract: A method for optimising a nucleotide sequence for protein expression in a host cell, comprising the steps of: (a) constructing an expression library comprising a large number of variants of the sequence to be expressed operatively cloned in an expression vector, wherein (i) the sequence of the 6 nucleotides immediately upstream (5?-direction) of the first codon of the coding sequence to be expressed is completely or partially randomized; (ii) the sequence of the second and third codons of the coding sequence to be expressed is randomized, wherein the randomization of the second and third codons is limited to changes not altering the amino-acids encoded by said codons; (b) screening the library with regard to efficiency of protein expression in the host cell; and (c) selecting a sequence resulting in a desired level of efficiency of protein expression.