Ran binding proteins (RanBPs) are highly conserved members of the GTP-binding protein family that are involved in nuclear protein export between the nucleus and the cytoplasm. In this study, a CmRanBP gene from a melon was isolated (Cucumis melo L.) using the RACE (rapid amplification of cDNA ends) method. The 778 basepair long melon, with a RanBP cDNA encoding consisting of 197 amino acids (22.2 kDa protein), was characterized (GenBank accession no: EU853459). The predicted amino acid sequence of CmRanBP was found to be 70% identical to VvRanBP, PtRanBP, and RcRanBP from Vitis vinifera, Populus trichocarpa, and Ricinus communis, respectively. Within the RanBD (Ran binding domain), 5 highly conserved motifs and 1 Ran binding motif were found in all members of the RanBP gene family from various plant species. Expression profiles of the CmRanBP gene in different tissues under high temperature stress were also investigated by semiquantitative RT-PCR. The CmRanBP gene was expressed in a similar manner in the roots, leaves, and stems at 25 degrees C as a control environment. However, when the temperature was raised to 38 degrees C and 40 degrees C, expression levels of the CmRanBP gene were significantly (P < 0.05) increased in the root, leaf, and stem tissues. We show here for the first time that the CmRanBP gene expression was correlated with heat stress responses.