Nucleotide sequence of equine MxA cDNA.

The researchers were successful in isolating a particular type of cDNA from the white blood cells of a horse after it had been stimulated by Interferon-alpha. They found that this cDNA has similarities with known mammalian Mx proteins and they named it equine MxA.

Isolation of cDNA

• The researchers created a cDNA library from the white blood cells (leukocytes) of a horse after they had been stimulated by a protein called Interferon-alpha.
• Through this process, they were able to isolate a 2.6 kb (kilobases) cDNA species. cDNA, also known as complementary DNA, is synthesized from a messenger RNA template through a process called reverse transcription. Its length is measured in kilobases.

Equine MxA cDNA characteristics

• This isolated cDNA has a single open reading frame (ORF), which indicates the portion of the gene that potentially encodes a protein. In this case, the ORF could potentially encode a 660 amino acid polypeptide.
• The researchers determined the nucleotide sequence of this cDNA, which identifies the exact order of nucleotides (adenine, thymine, guanine, and cytosine – the building blocks of DNA and RNA) in a DNA molecule.

Comparison with mammalian Mx proteins

• This cDNA shows a high degree of homology (similarity) with previously known mammalian Mx proteins, indicating a close genetic relationship. Mx proteins are part of the interferon system and protect cells against viral infections.
• Like other Mx proteins, this cDNA also possesses three consensus GTP-binding motifs. These are specific nucleotide sequences found in genes that allow them to bind to Guanosine triphosphate (GTP), a molecule that provides energy for many cellular processes.

Equine MxA nomenclature and properties

• The protein that the cDNA encodes has a calculated pI (isoelectric point) of 6.1. The isoelectric point is the pH point at which a particular molecule or surface has a net zero (neutral) charge.
• The researchers adhered to the proposed nomenclature and named this cDNA as equine MxA, identifying it as a specific type of Mx protein found in horses.