Rongqi Jia Yes, a point mutation can affect protein expression in several ways. Aminoacid substitution, Nonsense Mutation, silent mutation. while some point mutations might not significantly affect the protein, others can have substantial impacts on both the quantity and quality of the protein produced.

We need to be careful of precise meanings. I think it will be very rare that a point mutation would affect the Rate of Expression, however many point mutations do have a destabilizing affect on the protein and affect its turnover resulting in reduced accumulation of the protein. So it is quite common that a point mutation would decrease the amount of protein found at steady state even if the protein was expressed / produced at the wild type rate.

What this means is that playing with induction conditions is not likely to have much impact, but things that stabilize protein, such as lower temperatures, might. I would see if you have more luck at 25oC or even 16oC.

Yep, it can happen, I've seen it while doing Ala scans -some mutations for whatever reason produce large decreases in accumulated protein at steady state. Structural destabilization, as pointed out by Michael J. Benedik is one possible cause; if a structure for your protein is available, perhaps it'd be wise to check if folding deltaG has increased too much...you can try FoldX, for instance (https://foldxsuite.crg.eu/).

There are other possibilities, however (I'm assuming you are doing cytoplasmic expression in E. coli):

Hope it helps!

It depends mutation in intron or exons part.