Purification and properties of a brain-specific protein, human 14-3-3 protein.

of brain extract with, e.g. skeletal-muscle extract and comparing the pattern produced by the mixture with each organ electrophoresed separately but in parallel. At least three ‘constellations’ of protein spots appear to be present in all organs examined. The identity of these proteins is unknown. Several individual proteins, e.g. tubulin and actin, are also seen in all organs. At least eight proteins appear to be present in brain at relatively high concentrations (i.e. form prominent spots), but are absent from other organs. Four of these brain-specific proteins were identified as 14-3-2 protein, creatine kinase-BB, aldolase C, and 14-3-3 protein. The identity of the remaining four is unknown. The high resolution offered by current two-dimensional techniques presents considerable analytical difficulties and no attempt has been made to analyse the tissue distribution of the numerous fainter spots present on the electrophoretogram. It is unlikely that a majority of total brain proteins is being examined, first because only soluble proteins were selected and secondly because the two-dimensional system used is inadequate for the analysis of more basic proteins, probably due to gradient collapse at the alkaline and of the first dimension gel (O’Farrell, 1975). Even with the above limitations the system clearly has great potential as a means of detecting human tissue-specific proteins. We are grateful to Dr. N. L. Anderson and Dr. N. G. Anderson for much helpful advice. This work was supported by a grant from the Wellcome Trust to Professor C. N. Hales.