期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1973
卷号：70
期号：7
页码：2124-2128
DOI：10.1073/pnas.70.7.2124
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Apolipoprotein-alanine is an apolipoprotein isolated from very-low-density lipoproteins of human plasma. This protein contains 79 amino acids and binds phosphatidyl choline. Four fragments of this molecule corresponding to sequence positions 41-79 (I), 48-79 (II), 55-79 (III), and 61-79 (IV) have been synthesized by standard solid-phase methods. The resulting peptides were cleaved from the resin and deblocked with liquid HF, then purified by chromatography on Sephadex G-50 and DEAE-cellulose. Each purified peptide eluted as a single, symmetrical peak, exhibited a single band on polyacrylamide gel electrophoresis, and gave an amino-acid analysis in good agreement with the theoretical value. Circular dichroism studies indicated that only fragments I and II became more helical in the presence of phosphatidyl choline and significantly inhibited the reactivation of delipidated {beta}-hydroxybutyrate dehydrogenase (EC 1.1.1.30 ), an enzyme that requires phosphatidyl choline for activity. When subjected to ultracentrifugation at density 1.064 g/ml in the presence of phosphatidyl choline, fragments I, II, III, and IV floated to the top of the tube to the extent of 85, 50, 13, and 9%, respectively. These results indicate that residues 55-79 do not contain the minimum determinants required for the binding of phospholipid. However, extension of the peptide's N-terminus by seven residues produces a molecule that does bind phosphatidyl choline.
