Structure and interfacial properties of chicken apolipoprotein A-IV

• Published in: Journal of lipid research Vol. 41; no. 9; pp. 1410 - 1418
• Main Authors: Weinberg, R B, Anderson, R A, Cook, V R, Emmanuel, F, Denefle, P, Hermann, M, Steinmetz, A
• Format: Journal Article
• Language: English
• Published: United States Elsevier 01.09.2000
• Subjects: Air; Animals; Apolipoproteins A - chemistry; Chickens; Circular Dichroism; fluorescence; Humans; interfacial elasticity; molecular evolution; monolayers; Protein Denaturation; Recombinant Proteins - chemistry; spectroscopy; Surface Properties; surface tension; Thermodynamics; Water
• ISSN: 0022-2275; 1539-7262
• DOI: 10.1016/S0022-2275(20)33453-2

To gain insight into the evolution and function of apolipoprotein A-IV (apoA-IV) we compared structural and interfacial properties of chicken apoA-IV, human apoA-IV, and a recombinant human apoA-IV truncation mutant lacking the carboxyl terminus. Circular dichroism thermal denaturation studies revealed that the thermodynamic stability of the alpha-helical structure in chicken apoA-IV (DeltaH = 71.0 kcal/mol) was greater than that of human apoA-IV (63.6 kcal/mol), but similar to that of human apoA-I (73.1 kcal/mol). Fluorescence chemical denaturation studies revealed a multiphasic red shift with a 65% increase in relative quantum yield that preceded loss of alpha-helical structure, a phenomenon previously noted for human apoA-IV. The elastic modulus of chicken apoA-IV at the air/water interface was 13.7 mN/m, versus 21.7 mN/m for human apoA-IV and 7.6 mN/m for apoA-I. The interfacial exclusion pressure of chicken apoA-IV for phospholipid monolayers was 31.1 mN/m, versus 33.0 mN/m for human A-I and 28.5 mN/m for apoA-IV. We conclude that the secondary structural features of chicken apoA-IV more closely resemble those of human apoA-I, which may reflect the evolution of apoA-IV by intraexonic duplication of the apoA-I gene. However, the interfacial properties of chicken apoA-IV are intermediate between those of human apoA-I and apoA-IV, which suggests that chicken apoA-IV may represent an ancestral prototype of mammalian apoA-IV, which subsequently underwent further structural change as an evolutionary response to the requisites of mammalian lipoprotein metabolism.