title: Structural studies on lipophorin, an insect lipoprotein.
abstract: An insect high density lipoprotein, lipophorin, can be rapidly isolated from larval Manduca sexta (tobacco hornworm) hemolymph by single vertical spin density gradient ultracentrifugation. The two apolipoproteins (Mr = 245,000 and 78,000; designated apoLp-I and apoLp-II, respectively) were readily dissociated and separated in 6 M guanidine HCl by gel permeation chromatography. ApoLp-I and apoLp-II showed no immunological cross-reactivity on electrophoretic blots of sodium dodecyl sulfate-polyacrylamide gels. ApoLp-I and apoLp-II from lipophorin of adult M. sexta behaved identically to their larval counterparts. Amino acid compositions of larval apoLp-I and apoLp-II were similar except with respect to tryptophan and cysteine; apoLp-I contained 32 residues/mol of tryptophan (1.5 mol%) and 22 residues/mol (1.1 mol%) of cysteine; apoLp-II contained 2 residues/mol of tryptophan (0.2 mol%) and 14 residues/mol of cysteine (2.1 mol%). In double immunodiffusion tests, antiserum against apoLp-I or whole lipophorin strongly precipitated lipophorin, while antiserum against apoLp-II caused only minor precipitation. This indicates relatively greater exposure of apoLp-I to the aqueous environment.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002352:Carrier Proteins / Q000302:isolation & purification*; D003429:Cross Reactions; D004591:Electrophoresis, Polyacrylamide Gel; D007106:Immune Sera; D005779:Immunodiffusion; D007814:Larva / Q000032:analysis; D007915:Lepidoptera / Q000032:analysis*; D008074:Lipoproteins; D008970:Molecular Weight; D009036:Moths / Q000032:analysis*
chemical_list: D000596:Amino Acids; D002352:Carrier Proteins; D007106:Immune Sera; D008074:Lipoproteins; C032830:lipophorin