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Multiple mRNA species for the precursor to an adenovirus-encoded glycoprotein: identification and structure of the
Abstract:
Early region 3 of the adenovirus type 2 genome encodes three proteins with molecular weights of 16,000, 14,500, and 14,000 (E2/16, E3/14.5, and E3/14). The E3/16 protein is the precursor to the E3/19 glycoprotein and is around 1500 daltons larger than the unglycosylated E3/19O protein. The E3/14.5 and E3/14 proteins are structurally related to each other but different from E3/16. Three mRNA species were identified for E3/16; all have common 5' ends with the same spliced region but with different 3' ends. E3/14 was translated from a 13S mRNA with the same 5' structure as the E3/16 mRNA but followed by a second spliced region with a different 3' end. A partial amino acid sequence was determined for E3/16 after radioactive labeling in vitro and this sequence can be aligned with a known DNA sequence. It contains a hydrophobic signal sequence, two presumptive glycosylation sites, and a hydrophobic region close to the COOH terminus.
Insights
Adenovirus type 2 early region 3 encodes three proteins, E3/16, E3/14.5, and E3/14. Researchers identified distinct mRNA species and determined a partial amino acid sequence for E3/16, revealing structural features.
Area of Science:
- Molecular Virology
- Genomics
- Protein Biochemistry
Background:
- Adenovirus type 2 early region 3 (E3) encodes multiple proteins.
- These proteins play roles in viral replication and host interaction.
- Understanding E3 gene expression and protein structure is crucial for virology.
Purpose of the Study:
- To characterize the proteins encoded by adenovirus type 2 early region 3.
- To identify and analyze the mRNA species involved in E3 protein synthesis.
- To determine the structural features of the E3/16 protein.
Main Methods:
- Analysis of protein molecular weights.
- Identification and characterization of mRNA species using Northern blotting or similar techniques.
- In vitro translation and radioactive labeling of proteins.
- Partial amino acid sequencing and DNA sequence alignment.
Main Results:
- Three E3 proteins were identified: E3/16 (16,000 Da), E3/14.5 (14,500 Da), and E3/14 (14,000 Da).
- E3/16 is a precursor to E3/19 glycoprotein.
- Distinct mRNA species were found for E3/16 and E3/14, with variations in splicing and 3' ends.
- Partial E3/16 sequence revealed a hydrophobic signal sequence, glycosylation sites, and a C-terminal hydrophobic region.
Conclusions:
- Adenovirus type 2 E3 region exhibits complex gene expression with multiple mRNA transcripts.
- The E3/16 protein possesses structural motifs indicative of a secreted or membrane-associated glycoprotein.
- Further structural and functional studies of E3 proteins are warranted.