alpha tubulin molecular weight problem
This is not so easy to answer, since alpha-tubulin has at 10 known genes in this family (data from Ensembl):


TUBA1A   tubulin, alpha 1a
TUBA1B   tubulin, alpha 1b
TUBA3E   tubulin, alpha 3e
TUBA3D   tubulin, alpha 3d
TUBA4A   tubulin, alpha 4a
TUBAL3   tubulin, alpha-like 3
TUBA1C   tubulin, alpha 1c
TUBA3C   tubulin, alpha 3c
TUBA8    tubulin, alpha 8
TUBAL3   tubulin, alpha-like 3


You can go on the site linked above and choose any of the proteins. I checked TUBA1A, and get a length of 451 amino acids and a weight of approximately 50,1 kDa.