Human adenosine deaminase. cDNA and complete primary amino acid sequence

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Adenosine deaminase (ADA) is a critical enzyme in purine metabolism.
• Deficiency in ADA causes severe combined immunodeficiency (SCID), a primary immunodeficiency disorder.
• Previous studies had only isolated a partial cDNA sequence for human ADA.

Purpose of the Study:

• To obtain the complete cDNA sequence of human adenosine deaminase.
• To determine the full amino acid sequence and predict the secondary structure of ADA.
• To investigate ADA mRNA expression in patients with ADA-deficient SCID.

Main Methods:

• Cloning of additional nucleotide sequences using a previously isolated partial ADA cDNA insert.
• Construction of full-length cDNA encompassing coding and untranslated regions.
• Deduction of amino acid sequence from cDNA and protein sequencing.
• Secondary structure prediction analysis.
• Northern blot analysis to assess ADA mRNA levels.

Main Results:

• The complete coding and untranslated regions of human ADA cDNA were obtained.
• The full amino acid sequence of ADA was determined, comprising 362 amino acids (Mr = 40,638).
• Secondary structure prediction classified ADA as an alpha/beta protein.
• Northern blot analysis revealed normal to elevated ADA mRNA levels in B-lymphoblasts from ADA-deficient SCID patients.

Conclusions:

• The complete cDNA and amino acid sequence of human ADA have been elucidated.
• This detailed sequence information is essential for understanding the molecular basis of ADA deficiency.
• Further research can now focus on defining specific genetic abnormalities and their functional impact in ADA expression defects.