Instead, it contains a slightly different type of submune we call gamma one and gamma two. Now, what's the major difference between the beta and the gamma subunits? Well, as it turns out, in the gamma subunit, the gamma subunit does not have histidine 143. Instead of histidine 143, histidine is replaced with serene. And serene, as we know, does not have a positive charge. So serine is neutral.