UNLABELLED: The habitat of bioinorganic motifs (BIMs) is at the interface of biological inorganic chemistry and bioinformatics. BIM is defined as a common structural feature shared by functionally related, but not necessarily homologous, proteins, and consisting of the metal atom(s) and first coordination shell ligands. BIMs appear to be suitable for classification of metal centres at any level, from groups of unrelated proteins with similar function to different functional states of the same protein, and for description of possible evolutionary relationships of metalloproteins. However, they have not attracted wide attention from the bioinformatics community. Although their presence is appreciated, they are difficult to predict-therefore the current 'high-throughput' initiatives are likely to miss or ignore them altogether. The protein sequence databases do not distinguish between proteins containing different prosthetic groups (unless they have different sequences) or between apo- and holoprotein. On the other hand, the protein structure databases include data on 'hetero compounds' of various origin but these data are often inconsistent. A number of specialized databases dealing with BIMs and attempts to classify them are reviewed. SUPPLEMENTARY INFORMATION: The additional bibliography and list of Internet resources on bioinorganic chemistry are available at http://www.ebi.ac.uk/ approximately kirill/biometal/

To facilitate access to electronic resources for all researchers working in the field of P450 proteins and P450-containing systems, a WorldWide Web server has been established called The Directory of P450-containing Systems at < http://www.icgeb.trieste.it/p450/ >. Currently it contains the most up-to-date list of sequences of both the P450 superfamily and proteins mediating electron transfer to P450, i.e. NADPH:P450 reductases, specific NAD(P)H:ferredoxin reductases, cytochrome b5 reductases, ferredoxins and cytochromes b5, and their homologues from different enzyme systems. All the referenced sequences are provided with accession numbers and cross-links to major sequence databanks: PIR, SWISS-PROT, EMBL/GenBank and PRF.