Abstract
Apolipoprotein A-I (apoA-I), the major protein of high density lipoproteins, facilitates reverse cholesterol transport from peripheral tissue to liver. To determine the structural motifs important for modulating the in vivo catabolism of human apoA-I (h-apoA-I), we generated carboxyl-terminal truncation mutants at residues 201 (apoA-I201), 217 (apoA-I217), and 226 (apoA-I226) by site-directed mutagenesis. ApoA-I was expressed in Escherichia coli as a fusion protein with the maltose binding protein, which was removed by factor Xa cleavage. The in vivo kinetic analysis of the radioiodinated apoA-I in normolipemic rabbits revealed a markedly increased rate of catabolism for the truncated forms of apoA-I. The fractional catabolic rates (FCR) of 9.10 +/- 1.28/day (+/- S.D.) for apoA-I201, 6.34 +/- 0.81/day for apoA-I217, and 4.42 +/- 0.51/day for apoA-I226 were much faster than the FCR of recombinant intact apoA-I (r-apoA-I, 0.93 +/- 0.07/day) and h-apoA-I (0.91 +/- 0.34/day). All the truncated forms of apoA-I were associated with very high density lipoproteins, whereas the intact recombinant apoA-I (r-apoA-I) and h-apoA-I associated with HDL2 and HDL3. Gel filtration chromatography revealed that in contrast to r-apoA-I, the mutant apoA-I201 associated with a phospholipid-rich rabbit apoA-I containing particle. Analysis by agarose gel electrophoresis demonstrated that the same mutant migrated in the pre-beta position, but not within the alpha position as did r-apoA-I. These results indicate that the carboxyl-terminal region (residue 227-243) of apoA-I is critical in modulating the association of apoA-I with lipoproteins and in vivo metabolism of apoA-I.
Highlights
Apolipoprotein A-I, the major protein of high density lipoproteins, facilitates reverse cholesterol transport from peripheral tissue to liver
The concentration of plasma high density lipoproteins (HDL)1 is inversely related to the risk of developing human cardiovascular disease [1,2,3]
Reported to be an important ligand in the binding ofHDL to cell membranes [8, 9]. All these properties are important in the ability of Apolipoprotein A-I (apoA-I) to facilitate reverse cholesterol transport, the mechanism that has been proposed to account for the protective effect of HDL on cardiovascular disease
Summary
Vol 270, No 10, Issue of March 10, pp. 5469-5475, 1995 Printed in U.S.A. Carboxyl-terminal Domain Truncation Alters Apolipoprotein A-I in Vivo Catabolism*. Structural analysis revealed that the carboxyl-terminal region of apoA-I plays an important role in lipid binding and in the interaction of HDL with cell membranes [9, 19,20,21]. To address the role of structural motifs of apoA-I in its metabolic clearance, we have produced carboxyl-terminal truncation mutants of apoA-I and analyzed their metabolic clearance in vivo. These studies establish the importance of the carboxyl-terminal domain of apoA-I in its association with lipoprotein particles and catabolism
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
