You can check your total protein concentration by bradford and choose you concentration protein by dot blot protocol.

https://www.abcam.com/en-us/technical-resources/protocols/dot-blot?srsltid=AfmBOopWV-UX0JltuLAen-Ar4zg30enTewexLtZDa-_JlTadyO1wE5di

For the step transfert on membrane and Western Blot, you use a control with pure protein or similar size.

Hello Beatriz Piniella

Regarding the protein concentration to be loaded on SDS PAGE gel for Western Blot, it is typically between 10–40μg. However, the ideal concentration will depend on the protein and the sample. For instance, if the protein is in low abundance, you'll need to load more protein.

Also, loading too little protein may lead to an incomplete picture of the target protein, and loading too much protein can cause smears or streaks due to protein precipitation or aggregation.

Other considerations that you should take into account for such a large protein is provided in the link below.

https://www.researchgate.net/post/How_to_increase_the_efficiency_of_high_molecular_weight_proteins_in_western_blot_technique

Best.

for SDS-PAGE with Tris-glycine-SDS running and tris-glycine transfer buffer. use more ethanol in the transfer buffer, like 20%. and transfer overnight with cooling packs/ice and in a cold room. use a low % gel like 4%. make sure you are activating your membrane with Methanol if using PVDF!