Isolation and characteristics of mRNPs associated with bound polyribosomes from the ewe lactating mammary gland

Area of Science:

• Molecular Biology
• Biochemistry
• Cell Biology

Background:

• Polyribosomes are key structures for protein synthesis in eukaryotic cells.
• Messenger Ribonucleoprotein particles (mRNPs) are complexes of mRNA and proteins involved in gene expression regulation.

Purpose of the Study:

• To isolate and characterize mRNPs from the lactating mammary gland of ewes.
• To investigate the RNA and protein components of these mRNPs and their role in milk protein synthesis.

Main Methods:

• Dissociation of bound polyribosomes using EDTA or Puromycin-KC1 treatment.
• Sucrose gradient centrifugation to isolate and analyze mRNPs.
• Analysis of RNA components using cell-free protein synthesis systems.
• Protein component analysis using SDS-PAGE to determine molecular weights.

Main Results:

• EDTA or Puromycin-KC1 treatment released 22S mRNPs from ewe lactating mammary gland polyribosomes.
• RNAs isolated from mRNPs sedimented between 9S and 15S and directed milk protein synthesis in reticulocyte systems.
• The mRNP protein moiety comprised two major polypeptides (52,000 and 72,000 daltons) and two minor polypeptides (58,000 and 60,000 daltons).

Conclusions:

• Specific mRNPs containing functional milk protein-coding RNAs and distinct protein components are present in the lactating ewe mammary gland.
• These mRNPs play a crucial role in the post-transcriptional regulation of milk protein synthesis.