GI stands for "glycemic index." Seeing as most protein sources are very-low to carb-free, their GI is accordingly very low. They will have little immediate impact on blood sugar, which is what the GI measures. Of course, if you are relying upon protein catabolism as a glucose source, then eventually gluconeogenesis will begin to have an affect on your serum glucose, but this will not typically have a significant effect on insulin.
If what you are looking for is how fast protein's digest, that is an entirely different ballgame from GI. The density, size and amount of protein is going to determine how long it takes to digest. Small hydrolysates will be fastest as they are typically delivered in solution and are short in length. Protein isolates will usually be the next fastest, ranging from Whey taking about 40min to hit serum IIRC to Casein hitting at about the same time but remaining in serum much, much longer. Meat proteins typically take longer to reach the bloodstream than whey/casein, and are cleared sooner than casein most of the time.
I suggest you look up the Insulin Index.