Fig. 2.

The length of the polyglutamine tract modulates calpain cleavage of Htt. A, Cleavage of in vitro-translated Htt 3949-15 with m-calpain produced three distinct cleavage products, whereas the cleavage of Htt 3949-138 produced only a small amount of the largest calpain repeat-dependent cleavage product and barely detectable levels of the two smaller repeat-dependent cleavage products. B, Incubatingin vitro-translated Htt (Htt 3949-15 and Htt 3949-138) with increasing concentrations of m-calpain demonstrated that the 92 kDa cleavage product derived from mutant Htt is more rapidly produced and degraded at lower enzyme concentrations than the corresponding 72 kDa wild-type Htt cleavage product (n = 3).C, In the presence of m-calpain (30 nm), expanded Htt (Htt 3949-138) is preferentially cleaved relative to the normal protein (Htt 3949-15) (n = 3).