On 2017 May 18, Misha Koksharov commented:

FYI:

In contrast to Luciola mingrelica luciferase, in Photinus pyralis luc the homologous mutation Y33H doesn't affect pH-sensitivity of its color (at least there are no any differences in E. coli colonies compared with WT Ppy). Apparently, something is different in the surrounding interactions (it's not particularly surprising given the 67% sequence identity between the P. pyralis and L. mingrelica luciferases).

Regarding this region of the 3D structure, the mutation D234G in Ppy luc comes to mind: it makes Ppy luc quite pH-resistant (hence, greenish colony color with low pH-dependent shift); however, in the fully pH-sensitive L. mingrelica luc the corresponding residue is already G236.

On 2017 May 18, Misha Koksharov commented:

FYI:

In contrast to Luciola mingrelica luciferase, in Photinus pyralis luc the homologous mutation Y33H doesn't affect pH-sensitivity of its color (at least there are no any differences in E. coli colonies compared with WT Ppy). Apparently, something is different in the surrounding interactions (it's not particularly surprising given the 67% sequence identity between the P. pyralis and L. mingrelica luciferases).

Regarding this region of the 3D structure, the mutation D234G in Ppy luc comes to mind: it makes Ppy luc quite pH-resistant (hence, greenish colony color with low pH-dependent shift); however, in the fully pH-sensitive L. mingrelica luc the corresponding residue is already G236.