Translationally controlled tumour protein <p>Mammalian translationally controlled tumour protein (TCTP) (or P23) is a protein which has been found to be preferentially synthesised in cells during the early growth phase of some types of tumour [<cite idref="PUB00000270"/>, <cite idref="PUB00004349"/>], but which is also expressed in normal cells. The physiological function of TCTP is still not known. It was first identified as a histamine-releasing factor, acting in IgE +-dependent allergic reactions. In addition, TCTP has been shown to bind to tubulin in the cytoskeleton, has a high affinity for calcium, is the binding target for the antimalarial compound artemisinin, and is induced in vitamin D-dependent apoptosis. TCTP production is thought to be controlled at the translational as well as the transcriptional level [<cite idref="PUB00007167"/>]. </p><p> TCTP is a hydrophilic protein of 18 to 20 kD. TCTPs do not share significant sequence similarity with any other class of proteins. Recently, the structure of TCTP was determined and exhibited significant structural similarity to the human protein Mss4, which is a guanine nucleotide-free chaperone of the Rab protein [<cite idref="PUB00007168"/>]. Close homologues have been found in plants [<cite idref="PUB00004553"/>], earthworm [<cite idref="PUB00000677"/>], <taxon tax_id="6239">Caenorhabditis elegans</taxon> (F52H2.11), Hydra, <taxon tax_id="4932">Saccharomyces cerevisiae</taxon> (YKL056c) [<cite idref="PUB00006584"/>] and <taxon tax_id="4896">Schizosaccharomyces pombe</taxon> (SpAC1F12.02c).</p>