What is role of maskin protein?

Answer 1

Maskin protein prevents eukaryotic mRNAs from being recruited to the ribosome prior to egg fertilization. In other words, maskin halts translation of certain mRNA until after fertilization.

In the 3' end of the mRNA there is an Untranslated Region (UTR) (often a rich A region) that does not code for amino acids of the protein. Instead regions of the UTR are binding sites for Cytoplasmic Poly A Element-Binding Protein (CPEB), which binds to maskin. (Other translation inhibitors have similar mechanisms.) This interaction acts to prevent assembly of translation of the mRNA initiation complex until after fertilization.

Upon fertilization, phosphorylation of CPEB causes it to undergo a conformational alteration and release from the UTR. Translation can then proceed.

Poly(A) binding protein (PBAP) is able to bind to the now open A-rich UTR. PBAP binds to the initiation factor eIF-4G, which is bound to eIF-4E, another initiation factor bound to the 5' cap on the 5' end of mRNA. This binding forms the characteristic loop structure of eukaryotic protein synthesis.

Sources:

Karp, Gerald C. Cell and Molecular Biology: Concepts and Experiments. edition 5

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