The complete sequence of a 40-kDa actin-modulating protein from the earthworm Lumbricus terrestris

The complete primary structure of a 40-kDa actin-modulating protein from the earthworm Lumbricus terrestris is presented. A muscle-specific cDNA library of the earthworm was constructed and screened with a specific DNA probe obtained by polymerase chain reaction considering information from peptide sequencing. A full-length clone with a coding region of 1098 bp was isolated. The deduced polypeptide sequence of 366 amino acids (41457 Da) reveals the segmental structure typical of both the 40-kDa and 80-kDa actin-modulating proteins. Prominent similarities to the 80-kDa protein gelsolin especially exist with respect to the first segment and to the C-terminal segment. The comparatively high nucleation efficiency of the earthworm actin modulator is probably determined by its third segment which seems to enable the earthworm actin modulator to bind a second G-actin molecule more tightly than other previously described 40-kDa modulators.