A full-length cDNA clone encoding chaperonin 10 (cpn10) from a HeLa cell cDNA library was isolated: The cDNA is 538 bp in length, contains an ATG codon and a putative polyadenylation signal, and specifies a protein of 102 amino acids. Immunoprecipitation experiment showed that this human cpn10 has an apparent molecular mass of 11 kDa in sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE).