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cDNA cloning of human apoA-I: amino acid sequence of preproapoA-I
Abstract:
ds-cDNA to human liver apoA-I mRNA has been cloned. Nucleic acid sequence analysis revealed that apoA-I mRNA codes for a precursor apolipoprotein, preproapoA-I, which contains 24 amino acids on the NH2-terminal end of the mature plasma apoA-I. Eighteen amino acids are contained within the hydrophobic prepeptide (Met-Lys-Ala-Ala-Val-Leu-Thr-Leu-Ala-Val-Leu-Phe-Leu-Thr-Gly-Ser-Gln-Ala) followed by a 6 amino acid propeptide (Arg-His-Phe-Trp-Gln-Gln). Our results on human apoA-I are in agreement with the partial sequence of the precursor of rat apoA-I with respect to the length of the precursor sequence, location of the prepeptide, and the presence of an unusual propeptide sequence terminating in a neutral dipeptide Gln-Gln. A detailed analysis of the primary structure of normal human apoA-I mRNA will be essential to our ultimate understanding of the processing of human apoA-I and diseases characterized by molecular defects in apoA-I structure and function.
Insights
Scientists cloned complementary DNA (cDNA) to human liver apolipoprotein A-I (apoA-I) mRNA. This revealed apoA-I mRNA codes for a precursor, preproapoA-I, with a hydrophobic prepeptide and an unusual propeptide.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- Apolipoprotein A-I (apoA-I) is crucial for high-density lipoprotein (HDL) function.
- Understanding apoA-I precursor processing is vital for studying related diseases.
Purpose of the Study:
- To clone and analyze the complementary DNA (cDNA) sequence of human liver apoA-I mRNA.
- To elucidate the structure of the apoA-I precursor protein, preproapoA-I.
Main Methods:
- Complementary DNA (cDNA) cloning of human liver apoA-I mRNA.
- Nucleic acid sequence analysis.
Main Results:
- Human apoA-I mRNA encodes a precursor protein, preproapoA-I.
- PreproapoA-I consists of a mature apoA-I sequence preceded by a 24-amino acid N-terminal extension.
- This extension includes an 18-amino acid hydrophobic prepeptide and a 6-amino acid propeptide, with a Gln-Gln C-terminus.
Conclusions:
- The primary structure of human preproapoA-I has been determined.
- Findings align with rat apoA-I precursor sequences, particularly the unusual propeptide.
- Detailed analysis of human apoA-I mRNA structure is essential for understanding apoA-I processing and associated diseases.