Membrane proteins are crucial for biological processes, and many of them are important
to drug targets. Understanding the three-dimensional structures of membrane proteins are essential
to evaluate their bio-function and drug design. High-purity membrane proteins are important for
structural determination. Membrane proteins have low yields and are difficult to purify because
they tend to aggregate. We summarized membrane protein expression systems, vectors, tags, and
detergents, which have deposited in the Protein Data Bank (PDB) in recent four-and-a-half years.
Escherichia coli is the most expression system for membrane proteins, and HEK293 cells are the
most commonly cell lines for human membrane protein expression. The most frequently vectors
are pFastBac1 for alpha-helical membrane proteins, pET28a for beta-barrel membrane proteins,
and pTRC99a for monotopic membrane proteins. The most used tag for membrane proteins is the
6×His-tag. FLAG commonly used for alpha-helical membrane proteins, Strep and GST for beta-
barrel and monotopic membrane proteins, respectively. The detergents and their concentrations
used for alpha-helical, beta-barrel, and monotopic membrane proteins are different, and DDM is
commonly used for membrane protein purification. It can guide the expression and purification of
membrane proteins, thus contributing to their structure and bio function studying.