[show abstract][hide abstract] ABSTRACT: Melusin is a muscle specific protein required for heart hypertrophy in response to mechanical overload. Here we describe a protein 63% homologous to melusin, named chp-1, expressed in all tissues tested, including muscles, and highly conserved from invertebrates to human. Both proteins are characterized in their N-terminal half by a tandemly repeated zinc binding 60 amino acid domain with a motif of uniquely spaced cysteine and histidine residues. These motives are highly conserved from plants to mammals and have been recently named CHORD (for cysteine and histidine rich domain) domains. At the C-terminal end melusin contains a calcium binding stretch of 30 acidic amino acid residues which is absent in chp-1. While invertebrate genome contains only one gene coding for a chp-1 homolog, two genes coding for CHORD containing proteins (chp-1 and melusin) are present in vertebrates. Sequence analysis suggests that the muscle specific CHORD containing protein melusin originated by a gene duplication event during early chordate evolution.