Tools to enhance biochemistry undergraduate laboratory exercises using Escherichia coli beta‐galactosidase

Abstract

Our undergraduate biochemistry program has developed a comprehensive one‐semester laboratory course based on the E. coli β‐galactosidase enzyme. The rationale for this central theme is that students perceive more connections between different techniques or instruments with concepts that build upon foundational material in undergraduate biochemistry and microbiology courses. Two bio‐materials have proven critical to these exercises. The first is use of the E. coli ML308 (ATCC 15224) which is constitutive for β‐galactosidase expression. This strain is used to provide students with consistently high levels of expression for enzyme kinetics and inhibition experiments. The second biomaterial is a plasmid (Novagen Cat. No. 69257‐0.2ml) that contains the β‐galactosidase coding sequence inserted into pET15b with a 6X His‐tag on the N‐terminus. Experiments with this plasmid allow students to explore the kinetics of induction with lactose or IPTG, and also exposes them to affinity chromatographic procedure through a one step purification of the enzyme using affinity resin binding to the 6x His‐tag.