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Lipoprotein transformations during adipokinetic hormone action in Locusta migratoria
Author(s) -
GOLDSWORTHY GRAHAM J.,
MILES COLIN M.,
WHEELER COLIN H.
Publication year - 1985
Publication title -
physiological entomology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.693
H-Index - 57
eISSN - 1365-3032
pISSN - 0307-6962
DOI - 10.1111/j.1365-3032.1985.tb00030.x
Subject(s) - biology , adipokinetic hormone , lipoprotein , mole , glycoprotein , hemolymph , acrididae , size exclusion chromatography , biochemistry , concanavalin a , cholesterol , medicine , endocrinology , orthoptera , in vitro , enzyme , receptor , ecology , neuropeptide
. Detailed studies of lipoprotein A + formation during AKH action have been made in Locusta migratoria L. using gel filtration combined with the use of radiolabeled haemolymph protein probes. In addition, we have assessed the quantitative contribution of the C L ‐proteins to A + formation by direct measurement of the changes in concentration of free C L ‐proteins and report some properties of the C‐I and C‐II proteins: they appear to be glycoproteins of 20,000 and 16,000 MW respectively, but do not bind to concanavalin A. We have confirmed earlier observations (using different techniques) which showed that liproprotein A yellow is not involved per se in A + formation during the first 15 min of AKH action. In contrast, the (two) C L ‐proteins take part in A + formation without any apparent delay after hormone injection. Our observations show that A + formation is essentially complete within 30 min of AKH injection, although further C L ‐protein binding and lipid‐loading do occur subsequently. After 30 min there is no further decrease in the A yellow titre. It is argued that much, if not all, C L ‐protein is located at the surface of the A + particle. From the changes in titres which occur in A yellow and C L ‐proteins during AKH action we estimate that A + is formed from 1 mole of A yellow and approximately 28 moles of C L ‐proteins. Using these figures we calculate an apparent molecular weight for A + within the range of 1.65–2.12×10 6 , which is in reasonable agreement with estimates derived from gel exclusion chromatography data. These studies emphasize the dynamic and fully reversible nature of lipoprotein A + formation and highlight the complex nature of the lipoprotein transformations occurring during hormone‐stimulated lipid transport in locusts.