Human serum amyloid A (SAA): biosynthesis and postsynthetic processing of preSAA and structural variants defined by complementary DNA

• Published in: Biochemistry (Easton) Vol. 24; no. 12; pp. 2931 - 2936
• Main Authors: Sipe, J. D, Colten, Harvey R, Goldberger, G, Edge, M. D, Tack, B. F, Cohen, A. S, Whitehead, A. S
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.06.1985
• Subjects: Amino Acid Sequence; Amyloid - genetics; amyloid protein SAA; Base Sequence; Biological and medical sciences; cDNA; Cloning, Molecular; DNA - metabolism; Fundamental and applied biological sciences. Psychology; Genes. Genome; Genetic Variation; Humans; Liver - metabolism; man; Molecular and cellular biology; Molecular genetics; Molecular Weight; Nucleic Acid Hybridization; nucleotide sequence; Protein Processing, Post-Translational; RNA, Messenger - genetics; Serum Amyloid A Protein - biosynthesis; Serum Amyloid A Protein - genetics; signal peptides; Human; Proteins; Acute phase protein; Translation; Molecular processing; Complementary DNA; Liver; Genetic variant; Isolation; Serum; Oligonucleotide; Biosynthesis precursor
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00333a018

To study structural variants of human serum amyloid A (SAA), an apoprotein of high-density lipoprotein, complementary DNA clones were isolated from a human liver library with the use of two synthetic oligonucleotide mixtures containing sequences that could code for residues 33-38 and 90-95 of the protein sequence. The SAA-specific cDNA clone (pA1) contains the nucleotide sequence coding for the mature SAA and 10 amino acids of the 18-residue signal peptide. It also includes a 70 nucleotide long 3'-untranslated region and approximately 120 bases of the poly(A) tail. The derived amino acid sequence of pA1 is identical with the alpha form of apoSAA1. A fragment of pA1 containing the conserved (residues 33-38) region of SAA also hybridized with RNA from human acute phase liver and acute phase stimulated, but not unstimulated, mouse and rabbit liver. In contrast, a fragment corresponding to the variable region hybridized to a much greater extent with human than with rabbit or murine RNA. Human acute phase liver SAA mRNA (approximately 600 nucleotides in length) directs synthesis of preSAA (Mr 14 000) in a cell-free translating system. In a Xenopus oocyte translation system preSAA is synthesized and processed to the mature Mr 12 000 product. The complete 18 amino acid signal peptide sequence of preSAA was derived from sequencing cDNA synthesized by "primer extension" from the region of SAA mRNA corresponding to the amino terminus of the mature product. Two other SAA-specific cDNA clones (pA6 and pA10) differed from pA1 in that they lack the internal PstI restriction enzyme site spanning residues 54-56 of pA1.