ABSTRACT
In 1990, Hartmut Michel edited a book that serves still today as a useful reference for methodology and background when attempting to crystallize membrane proteins.1 At that time, the structure of 400 proteins was known at, or nearly at, atomic resolution. However, only two of these were membrane proteins: the bacterial reaction centre from Rhodopseudomonas viridis2 and bacteriorhodopsin from Halobacterium salinarum.3 At the time of writing, the number of structures deposited in the Research Collaboratory for Structural Bioinformatics (RCSB) Data Bank had grown to 32,600, and yet the number of known membrane proteins amounts to no more than 58, of which only 26 can be classed as unrelated. A thorough and regularly updated list of all membrane protein structures, along with
a tabulation of the crystallization conditions, is maintained at the following Web site: www.mpibp-frankfurt.mpg. de/michel/public/memprotstruct.html.
