PURIFICATION AND CHARACTERIZATION OF 2 STORAGE PROTEINS FROM LOCUSTA-MIGRATORIA SHOWING DISTINCT DEVELOPMENTAL AND HORMONAL-REGULATION

Two major hemolymph proteins, belonging to the insect hexameric storag e protein family, have been purified from Locusta migratoria. Larval s torage protein 1 (LSP1) has M(r) = 410,000, s = 16.1S, 10% hexose cont ent and is composed of up to five different 75 kDa subunits. Isoelectr ic focusing of native LSP1 shows a pi of about pH 6.0 with some microh eterogeneity. Persistent storage protein (PSP) has a M(r) = 460,000, s = 16.4S, 7% hexose and contains major 74 kDa and minor 77 kDa subunit s. Native PSP has a pI of pH 5.6 also with some microheterogeneity. PS P dissociates reversibly into monomers at alkaline pH. The N-terminal sequence was determined for the PSP 74 kDa subunit. A previously ident ified cyanoprotein (CP), with M(r) = 435,000 and subunits of 69 kDa, w as also purified. A second larval-specific storage protein, LSP2, has been identified but not purified. LSP1 and PSP exhibit distinct develo pmental patterns and hormonal regulation. LSP1 is larval-specific, inc reasing to a high concentration in the late fifth instar and disappear ing in the early adult. PSP, however, remains abundant through the las t larval instar and persists at a lower concentration in the adult. In fifth instar larvae, treatment with the juvenile hormone (JH) analog, pyriproxyfen, totally repressed production of LSP1, and significantly lowered the hemolymph level of PSP. In contrast, JH analog treatment is found to elevate the level of PSP in adults. Storage proteins which persist in the adult stage, under hormonal regulation that is switche d during metamorphosis, may be characteristic of some hemimetabolous i nsects. Copyright (C) 1996 Published by Elsevier Science Ltd.