Molecule of the Month: Golgi Casein Kinase
Casein and many other secreted proteins are phosphorylated by Golgi casein kinase
Authentic Casein Kinase
Casein in Milk
Milk and Cheese
Exploring the Structure
Golgi casein kinase tends to add phosphate groups at locations in proteins with a characteristic sequence motif: S-X-E, where “S” is the serine to which the phosphate will be added, “X” can be anything, and “E” is a glutamate. The enzyme also works well if a previously phosphorylated serine is in the “E” position. PDB ID 2lid includes an example of this motif with a phosphate added. The protein is vitellogenin, a highly phosphorylated protein that is found in egg yolks. The example shown here is a similar vitellogenin from a wasp. To explore this structure in more detail, click on the image for an interactive JSmol.
Topics for Further Discussion
- You can compare the structures of Fam20C (chain B in 5yh2) and Fam20A (chain A in 5yh2) using the Pairwise Structure Alignment Tool. Also try aligning Fam20B (chain A in 5xoo).
- The PDB includes many structures of proteins with phosphorylated serine amino acids. To find them, look at the page for phosphoserine (SEP), and click on "is present in a polymer sequence".
Related PDB-101 Resources
- Browse Transport
- Worby, C.A., Mayfield, J.E., Pollack, A.J., Dixon, J.E., Bannerjee, S. (2021) The ABCs of the atypical Fam20 secretory pathway kinases. J Biol Chem 296: 100267
- Roy, D., Ye, A., Moughan, P.J., Singh, H. (2020) Composition, structure, and digestive dynamics of milk from different species. Front. Nutrition 7: 577759
- 5yh2: Zhang, H., Zhu, Q., Cui, J., Wang, Y., Chen, M.J., Guo, X., Tagliabracci, V.S., Dixon, J.E., Xiao, J. (2018) Structure and evolution of the Fam20 kinases. Nat Commun 9: 1218-1218
- 2lid: Havukainen, H., Underhaug, J., Wolschin, F., Amdam, G., Halskau, O. (2012) A vitellogenin polyserine cleavage site: highly disordered conformation protected from proteolysis by phosphorylation. J Exp Biol 215: 1837-184
January 2022, David Goodsellhttp://doi.org/10.2210/rcsb_pdb/mom_2022_1