Histories are DNA-binding proteins that assist in DNA packaging and protection. Here, we, for the first time, cloned a novel histone HI cDNA (638 bp) from the goldfish, Carassius auratus. Sequencing revealed that this histone HI shared 68.1% amino acid identity and 73.9% similarity with that from the rainbow trout, Salmo gairdneri. We successfully expressed a full-length recombinant version (similar to 20kDa) and a truncated C-terminal fragment (similar to 6 kDa; 61 amino acids) of this histone H1 as a partially soluble form using a maltose binding protein (MBP) fusion strategy in an Escherichia coli expression system. Our results revealed that both these recombinant histone H1 versions had DNA binding and protection functions, and MBP fusion system was an effective way to produce biological functional recombinant histone proteins in E. coli. This novel recombinant histone H1 protein and/or its C-terminal peptide could be used as potential mediators for efficacious gene delivery. (C) 2006 Elsevier Inc. All rights reserved.