First, sorry for the presumably trivial question but I have limited knowledge in this area. I want to cite two different studies that seem to provide different results or perhaps I just can't get the point. The first study claims that "after a 34 aa deletion from the central core of the linker region ATP hydrolysis and drug transport activities were completely abrogated, indicating that the linker deletion disconnected substrate binding from ATP hydrolysis and transport.". The second one claims "..linker cleavage increased ATPase activity." Thus I am confused.

How might these experiments be explained? Whats "happening" with the cleaved linker (75aa), does it just disappear? What is the main difference between these experimental approaches in above case?

http://pubs.acs.org/doi/abs/10.1021/bi9808823

http://www.ncbi.nlm.nih.gov/pubmed/19490125

http://www.jbc.org/content/277/33/29417.full