Regeneration of bacteriorhodopsin in mixed micelles

Regeneration of bacteriorhodopsin from bacterioopsin and all-trans-retinal was studied in a mixed micelle system consisting of dodecyl sulfate, CHAPS and a water-soluble phospholipid dihexanoylphosphatidylcholine (hex2-PhosChol). Regeneration to approximately 40,000 M-1.cm-1 extinction at 550 nm (epsilon 550) was obtained with either 2.3 mM or 6.5 mM CHAPS along with 6.9 mM dodecyl sulfate and 4.5 mM hex2-PhosChol in 0.16 M NaCl and 40 mM phosphate (pH 6.0). Without CHAPS, the regeneration in 4.5 mM Hex2-PhosChol gave epsilon 555 = 27,800; without PhosChol, the 1:3 CHAPS/dodecyl sulfate mixture gave epsilon 550 approximately 20,000; and without PhosChol the nearly equimolar CHAPS/dodecyl sulfate mixture gave epsilon 550 approximately 10,000. The composition of the mixed micelles was estimated from fluorescence spectroscopy using pyrene butyryl hydrazine. The molecular weight was estimated by molecular seive chromatography to be 87,100 for 2.3 mM CHAPS, 6.9 mM dodecyl sulfate and 0.67 mM hex2-PhosChol; and 83,200 for 7.0 mM CHAPS, 6.9 mM dodecyl sulfate, and 1.1 mM hex2-PhosChol. These results are consistent with the idea that at low concentrations of CHAPS and dodecyl sulfate, CHAPS organizes the dodecyl sulfate into disk shaped bilayer micelles that are favorable for bacterioopsin refolding. However, a high concentration of either detergent inhibits regeneration. Added hex2-PhosChol can overcome the inhibitory effects of high concentrations of either CHAPS or dodecyl sulfate.

Synthesis of human coagulation factor XIII in yeast

The active form of coagulation factor XIII, factor XIIIa, is a transglutaminase that covalently cross-links fibrin molecules by joining gamma-glutamyl and epsilon-lysyl primary amino groups. In this paper we report the design of a yeast expression vector called pPH3 which includes the GAL1-GAL10 promoter, multiple cloning sites, the URA3 selectable marker, the 2 mu sequences and the ampicillin-resistance gene. We have placed full-length factor XIII cDNA into the PstI site of this vector, transformed the yeast cells and expressed human coagulation factor XIII which was found to be enzymatically active based on observations that this recombinant factor XIII: (a) showed immunological identity with placental factor XIII; (b) was demonstrated to have transglutaminase activity, and (c) cross-linked fibrin in a manner identical to human placental factor XIIIa-catalyzed polymerization (gamma-gamma dimerization and alpha polymerization).