A mutated form of arm, lacking the end of the N-terminal region (amino acids 101-139 are deleted), is expressed under the control of its own promoter. The protein is tagged with a Tag:MYC epitope at residue 784 in the Gly/Pro-rich region close to the C-terminus. arm 3' trailer sequences are also present. The protein produced shows slightly reduced levels of binding to shg protein compared to wild-type controls in a coimmunoprecipitation assay and binding to α-Cat protein is abolished.