Abstract: The expression vectors and methods using an E. coli expression system for the large scale production of IL-21 are described. The vectors utilize the IL-21 coding sequence with specific changes in nucleotides in order to optimize codons and mRNA secondary structure for translation in E. coli. Using the expression vectors, the IL-21 gene was produced in E. coli to a level of greater than 1 g/L in fed batch fermentation. Also included are OmpT deficient E. coli strains transformed with an IL-21 expression vector.

Abstract: The expression vectors and methods using an E. coli expression system for the large scale production of IL-21 are described. The vectors utilize the IL-21 coding sequence with specific changes in nucleotides in order to optimize codons and mRNA secondary structure for translation in E. coli. Using the expression vectors, the IL-21 gene was produced in E. coli to a level of greater than 1 g/L in fed batch fermentation. Also included are OmpT deficient E. coli strains transformed with an IL-21 expression vector.

Abstract: A packing system for the operating stem of rotary valves includes first and second packing assemblies engaged with the stem at axially spaced locations. The first assembly is adjustably compressed into sealing engagement with the stem by a first packing nut which carries both the second packing assembly and a second packing nut for adjustably compressing the second packing assembly into sealing engagement with the stem independently of the first packing assembly. The space between the first and second packing assemblies provides a sealed chamber to allow detecting any leakage taking place from the valve chamber through the first stem packing assembly.