Combinations of synthetic polymers and natural proteins provide a route to the synthesis of new biomaterials. The bioconjugates combining tunable properties of polymers with functionalities of proteins have found broad applications. One of the most challenging problems in this research field is the self-assembly behaviors of responsive polymer protein bioconjugates. In this research, synthesis and self-assembly of bioconjugates composed of zwitterionic block copolymer and streptavidin were investigated. Block copolymers of poly(ethylene glycol) (PEG) and poly[3-dimethyl(methacryloyloxyethyl)ammonium propanesulfonate] (PDMAPS) with cleavable biotin groups at the junction points were synthesized. The zwitterionic block copolymers exhibit phase transitions with upper critical solution temperatures (UCSTs) in aqueous solutions. The concentration of sodium chloride exerts a significant influence on the UCST. The zwitterionic block copolymer chains self assemble into vesicles in aqueous solution at a temperature below UCST. Bioconjugates comprising of streptavidin molecules and zwitterionic block copolymer chains were fabricated based on biotin streptavidin coupling. Upon conjugation to the protein molecules, the UCST of the zwitterionic block copolymer decreases due to the screening effect of the protein molecules. The bioconjugates are able to make self-assembly into different structures, depending on the average number of block copolymer chains on a protein molecule. The bioconjugate molecules with average 1.3 block copolymer chains on a streptavidin self assemble into rodlike structures, while those with average 2.9 chains on a streptavidin self-assemble into spherical micelles.