There are, of course, several reasons for the structural revolution. One of them was that cloning techniques started to enter the lab, and the number of different proteins and their quantity available for crystallization increased drastically. Before the cloning era, proteins were purified directly from cells, which substantially limited availability − there is always a limited number of copies of a particular protein in a cell. Therefore, obtaining a few milligrams of protein for crystallization required large cell volumes. Cloning solved the problem; proteins could be expressed in large quantities and purified for crystallization. Another essential factor was the introduction of synchrotron radiation for X-ray data collection. Several synchrotrons worldwide currently provide high intensity X-rays for quality X-ray data collection. In addition, synchrotrons reduced the time required for the optimization of crystallization conditions.
In the early days of crystallography, we needed to optimize the crystallization conditions to grow crystals large enough for the relatively low-intensity laboratory X-ray sources. The third factor, I believe, was the introduction of low-cost personal computers with ever-increasing computational and graphics processing power. Cheaper computers also meant new software, which became much more user-friendly. In the middle of the 1980-ties, a proper graphics monitor with a computer, which was needed for model building and refinement, would cost around 100 k dollars, obviously unaffordable for personal use for people interested in science. Now a Windows PC or a Mac is all we need. Then came the era of structural genomics - large consortia were formed to develop new technologies for crystallization and solving large numbers of protein structures. With the increasing number of solved structures, the number of protein databases increased, and new tools for analyzing protein sequences and structures were rapidly developed.
Although the number of structures in the PDB is rapidly increasing, one should remember that far from all PDB entries are unique. There are many entries of the same protein in the database - some are mutant variants, others may be complexes with ligands (substrate analogs, inhibitors, cofactors), complexes with other proteins, etc. This may be a source of confusion when we try to fetch a structure from the PDB - which one to choose if there are many entries of the same protein? For our purposes, we also need to remember that not all structures in the PDB are created equal, and we need to identify the one with the best available quality (see discussion of structure quality
Using the PDB, we can easily find the structure of the protein of interest and assess its quality. We need to type the name of the protein into the search window on the PDB site. Generally, one gets many hits, some of which would be unrelated to the search. PDBsum and PDBe (PDB Europe) usually give more narrowed search results. It is also possible to refine the search using the options provided at the PDB site.
PDB, PDBe, and PDBsum provide plenty of additional data, including links to other databases where more information can be found. Below is an example from the PDBsum link page (for mobile view, please click here