DefinePK

Abstract

The basic Helix-Loop-Helix bHLH proteins are a family of transcription factors that are found in almost all eukaryotic genomes. This family of proteins regulates a variety of biological processes including embryonic development. Here we describe the catalog of human, mouse and rat bHLH proteins. Extensive in silico studies identified 121 human, 121 mouse and 120 rat bHLH proteins. Human has orthologs for 119 rat bHLH proteins. Two bHLH proteins are found only in human, while human lacks one rodent specific bHLH protein, MYCS. Fifty bHLH protein families are present in all three lineages. Forty nine bHLH proteins contain 16 additional domains. Orthologous bHLH pairs vary in sequence conservation along their length, creating a map of functionally important regions for every bHLH protein pair. Many species-specific sequence inserts exist. This study provides a comprehensive overview of bHLH proteins.