| Autor: |
van der Horst, Dick J., van Doorn, Jan M., Voshol, Hans, Kanost, Michael R., Ziegler, Rolf, Beenakkers, Ad M. Th. |
| Předmět: |
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| Zdroj: |
European Journal of Biochemistry; 3/14/91, Vol. 196 Issue 2, p509-517, 9p |
| Abstrakt: |
Insects transport lipid for flight in the form of diacylglycerol-rich low-density lipoproteins (low-density lipophorin, LDLp), which in the hemolymph are produced from high-density lipophorin (HDLp) by reversible association with several molecules of an apolipoprotein, apolipophorin III (apoLp-III, Mr ≈ 18000-20000) during lipid loading. Two isoforms of apoLp-III (a and b) were purified both from adult Locusta migratoria migratorioides hemolymph and LDLp, which have identical apparent Mr but differ in amino acid composition, NH2-terminal amino acid sequence, and isoelectric points (5.35 ± 0.01 for apoLp-IIIa, 5.10 ± 0.01 for apoLp-IIIb). The NH2terminal sequence of apoLp-IIIb is identical to the primary structure of apoLp-III deduced from cloned cDNA [Kanost et al. (1988) J. Biol. Chem. 263, 10568-10573], whereas the NH2-terminal sequence of apoLp-IIIa is identical to that of apoLp-IIIb but preceded by Arg-Pro-, which is the C-terminal of the putative signal peptide coded by cDNA upstream from that coding for apoLp-IIIb. The ratio apoLp-IIIa apoLp-IIIb free in hemolymph is identical to that in LDLp (5:9); since 14 molecules of apoLp-III appear to be bound in one molecule of LDLp, an average of 5 molecules of apoLp-IIIa and 9 of apoLp-IIIb are involved in formation of each LDLp particle. In vivo studies using 35S-labeled apoLp-IIIa and b demonstrate that each of the isoforms can associate with HDLp to produce LDLp reversibly; in an in vitro system, production of LDLp containing exclusively apoLp-IIIa or apoLp-IIIb demonstrates independent participation of each isoform in LDLp formation. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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