I'm using the RCSB's Rest API to gather some bond data information for metalloenzymes. I wanted to know whether the differing naming conventions for PDB IDs(some are letter-number-letter-number, while some are 3 numbers - 1 letter) signify anything, as in do they contain more/less information or are an older version(different format)?
They tend to be sequential for structures published together as part of the same study or project. They're automatically assigned now and contain no meaningful information by themselves other than that. Older structures appear to have been named with a bit more human input, e.g. the first near-complete structure of the ATP-binding domain of a protein kinase is 1ATP.