Protist, Vol. 150,257-264, October 1999 © Urban & Fischer Verlag http://www.urbanfischer.de/journals/protist ORIGINAL PAPER Protozoal Sequences may Reveal Additional Isoforms of the 14-3-3 Protein Family Protist Neil R. McEwan a ,1, Sylvain C. P. Eschenlauera, Roger E. Calza b , R. John Wallace a , and C. Jamie Newbold a aRowett Research Institute, Greenburn Road, Bucksburn, Aberdeen, AB21 9SB, Scotland bDepartments of Genetics and Cell Biology and Animal Sciences, Washington State University, Pullman, WA 9964- 630, USA Submitted February 23, 1999; Accepted August 1, 1999 Monitoring Editor: R. lain Wilson The phylogenetic position of eleven 14-3-3 proteins from five protozoal species was tested relative to other eukaryotic 14-3-3 versions representing many of the preViously described isoforms. The proto- zoal proteins, four from Entodinium caudatum, three from Entameoba histolytica and four from api- complexan parasites formed clusters closer to the plant and animal epsilon isoforms than to the ani- mal beta, gamma/eta, sigma/theta, and zeta isoforms. This extends the preliminary findings of Wang and Shakes (1996) but data from a wider range of genera are still required to strengthen our hypothe- sis that the protozoan isoforms may constitute novel isoforms of the 14-3-3 family. Introduction Proteins from the 14-3-3 family were first described in bovine brains (Moore and Perez 1967) and were initially thought to be brain specific proteins. They have since been described in a diverse range of other vertebrates, as well as in fruit flies, worms, fungi and a number of plants (reviewed in Aitken et al. 1992). In addition, they have now been described in a number of different tissues, and are thought to be ubiquitous among eukaryotes (Piotrowski and Oecking 1998). The proteins generally have a molecular mass of approximately 30kDa and in the functional form are found as dimers (Liu et al. 1995). Both animals and plants have been shown to possess a number of dif- ferent isoforms. In mammals, at least seven iso- 1 Corresponding author; fax 44-1224-715349 e-mail nrm@rrLsarLac.uk forms have been described, and although at least one isoform is cell specific, tissues can simultane- ously contain more than one form (Aitken et al. 1992). Piotrowski and Oecking (1998) have sug- gested that there are at least five different isoforms in plants. This can now be seen as an under-estima- tion, as Arabidopsis thaliana is known to contain at least nine different isoforms, on the basis of entries to GenBank. The initial function attributed to 14-3-3 was linked to the stimUlation of the calmodulin kinase II-depen- dent activation of tyrosine and tryptophan hydroxy- lases during the synthesis of serotonin and dop- amine (Ichimura et al. 1991). Since this original work, a range of different proteins has been identified hav- ing high homology to this family (Jarillo et al. 1994). These include cold inducible proteins (Jarillo et al. 1994), a factor involved in activation of a virulence factor of Pseudomonas aeruginosa (Fu et al. 1993) 1434-4610/99/150/03-257 $ 12.00/0