Lipid-peptideEnteraetisms between fragments of the transit peptide of ribulase-1,5bisphosphate sarboxgrlase/oxygsmase and chloroplast membrane lipids Received 5 August 1991The mteractlons of fragments of the transit peptide of r~bulose-I $blsphosphate carboxylase/oxygenase with hp~d monolayers was studied In order to mvestlgate the possible mvolvement of the membrane hplds m the pro&m Import peocess The fragments are surface active and have a differential ablhty to Insert m hpld monolayees The fragments have a preference for the chloroplast galacto-and sulphohplds and phosphatldylglycerol and Interact with envelope membrane hptd extracts These results suggest that probably transu peptlde-hpld InteractIons aec mvolvcd III the chloroplast protem Import process Chloroplast protem Import, Trdnslt peptlde, Pepttde-hpld mteractlon, Galactohpld. Sulphohpld, Small subumt of rlbulosc-l,5-blsphosphatr: carboxylaselovygenase

The aim of this study was to investigate whether long-circulating liposomes can improve the anti-inflammatory activity of superoxide dismutase (SOD). Small-sized poly(ethyleneglycol) (PEG)-liposomes containing SOD were prepared via different preparation protocols and characterized in terms of encapsulation efficiency (EE), size, enzymatic activity and protein structure, to establish conditions where high EE can be combined with preservation of enzyme activity and structure. It was observed that structural information from circular dichroism analyses does not correlate with data on enzyme activity. SOD-containing PEG-liposomes prepared by the dehydration-rehydration method appeared to represent the most attractive formulation for in vivo evaluation. The therapeutic potential of selected SOD-containing PEG-liposomes was established and compared with SOD entrapped in stearylamine (SA)-liposomes and 'free' SOD upon intravenous (i.v.) injection in an arthritic rat model. Both small PEG-liposomes and SA-liposomes showed a superior therapeutic activity compared to 'free' SOD, with PEG-liposomes inducing stronger anti-inflammatory effects than SA-liposomes.

Import of proteins into chloroplasts depends on an N-terminal transit sequence. Transit sequences contain little primary sequence similarity and therefore recognition of these sequences is thought to involve specific folding. To assess the conformational flexibility of the transit sequence, we studied the transit peptide of preferredoxin (trfd) by circular dichroism. In buffer, trfd is in a random coil conformation. A large increase in ~-helix was induced in the presence of micelles or vesicles formed by anionic lipids. Less pronounced changes in secondary structure were induced by zwitterionic detergents but no changes were observed in the presence of neutral detergents or vesicles composed of phosphatidylcholine.

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The interaction of the chloroplast precursor protein of ferredoxin with mixed model membranes composed of 'H chain labeled monogalactosyl diacylglycerol and phosphatidylcholine was studied by 'H and "P NMR. The bilayers were found to have special chain packing properties which most likely are the result of a specific arrangement of head groups at the interface. The precursor and not the corresponding apoprotein induced a bilayer+isotropic transition in lipid organization as a result of the transit sequence-lipid interaction. The implications of these observations for proteins import into chloroplasts are indicated.