Secondary structure of the pentraxin female protein in water determined by infrared spectroscopy: effects of calcium and phosphorylcholine

• Published in: Biochemistry (Easton) Vol. 31; no. 39; pp. 9364 - 9370
• Main Authors: Dong, Aichun, Caughey, Byron, Caughey, Winslow S, Bhat, Kolari S, Coe, John E
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 06-10-1992
• Subjects: Alpha-Globulins - chemistry; Alpha-Globulins - drug effects; Amino Acid Sequence; Animals; Biological and medical sciences; C-Reactive Protein; calcium; Calcium - pharmacology; Cricetinae; Cricetulus; effects on; female protein; Fundamental and applied biological sciences. Psychology; hamsters; I.R. spectroscopy; Molecular biophysics; Molecular Sequence Data; phosphorylcholine; Phosphorylcholine - pharmacology; Physico-chemical properties of biomolecules; Protein Structure, Secondary - drug effects; secondary structure; Sequence Homology, Amino Acid; Spectrophotometry, Infrared; Water; Infrared spectrometry; Calcium; Solution structure; Female protein; Binding site; Aqueous solution; Secondary structure
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00154a006

The secondary structure of hamster female protein in aqueous solutions in the presence or absence of calcium and phosphorylcholine has been investigated using Fourier transform infrared spectroscopy. Our present studies provide the first evaluation of the secondary structure of FP and its calcium- and phosphorylcholine-dependent conformational changes. Quantitative analysis indicated that FP is composed of 50% beta-sheet, 11% alpha-helix, 29% beta-turn, and 10% random structures. Calcium- and phosphorylcholine-dependent infrared spectral changes were observed in regions assigned to beta-sheet, alpha-helix, turn, and random structures. The infrared-based secondary structure compositions were used as constraints to compute theoretical locations for the different secondary structures along the amino acid sequence of the FP protein. Two putative calcium-binding sites were proposed for FP (residues 93-109 and 150-168) as well as other members of the pentraxin family on the basis of the theoretical secondary structure predictions and the similarity in sequence between the pentraxins and EF-hand calcium-binding proteins. The changes in protein conformation detected upon binding of calcium and phosphorylcholine provide a mechanism for the effects of these ligands on physiologically important properties of the protein, e.g., activation of complement and association with amyloids.