Patent ID: 8945855
Filing Date: 2015-02-03
Classification: C12N

Abstract:
1. A nucleic acid vector for engineering protease variants, wherein the nucleic acid vector encodes two separately expressed fusion proteins, wherein the first fusion protein comprise, in an N- to C-terminal direction: (i) a first endoplasmic reticulum (ER) targeting sequence; (ii) a surface expression sequence; (iii) a first peptide sequence that is a counterselection substrate sequence for the enzyme of the second fusion protein; (iv) a first epitope tag sequence; (v) a second peptide sequence that is a selection substrate sequence for the enzyme of the second fusion protein; (vi) a second epitope tag sequence; and (vii) a first endoplasmic reticulum (ER) retention sequence, wherein the second fusion protein comprises, in an N- to C-terminal direction: (viii) a second endoplasmic reticulum (ER) targeting sequence; (ix) an enzyme, wherein the enzyme is a protease; and (x) a second endoplasmic reticulum (ER) retention sequence.