The lobster carapace carotenoprotein, alpha-crustacyanin. A possible role for tryptophan in the bathochromic spectral shift of protein-bound astaxanthin.
Crustacyanin, cross-linked with dimethyl pimelimidate to stabilize the protein against denaturation, was used to test the effects of tryptophan modification with BNPS-skatole [3-bromo-3-methyl-2-(nitrophenylmercaptol)-3H-indole] on the ability of the apoprotein to recombine with astaxanthin. The cross-linked apoprotein re-forms alpha-crustacyanin with astaxanthin in reasonable yield following incubation of the protein under the conditions for tryptophan modification in the absence of BNPS-skatole. The BNPS-skatole-treated protein reconstitutes with astaxanthin to give a carotenoprotein with lambda max. at 472 nm, that of the carotenoid in hexane, in a yield similar to that of the BNPS-skatole-untreated control. The implied involvement of tryptophan residues at the sites of astaxanthin attachment in crustacyanin and their possible roles in the binding sites of vitamin A in vitamin A-proteins are discussed in relation to the bathochromic spectral shifts of the chromophores.
Zagalsky
P F
PF
Department of Biochemistry, Royal Holloway and Bedford New College, Egham, Surrey, U.K.
Eliopoulos
E E
EE
Findlay
J B
JB
D000818:Animals; D001059:Apoproteins / Q000378:metabolism; D001665:Binding Sites; D002338:Carotenoids / Q000378:metabolism*; D002352:Carrier Proteins; D004591:Electrophoresis, Polyacrylamide Gel; D008958:Models, Molecular; D008121:Nephropidae; D011487:Protein Conformation; D011506:Proteins / Q000302:isolation & purification / Q000378:metabolism*; D012862:Skatole / Q000031:analogs & derivatives / Q000494:pharmacology; D013053:Spectrophotometry; D014364:Tryptophan; D024341:Xanthophylls; D019207:beta Carotene / Q000031:analogs & derivatives*
D001059:Apoproteins; D002352:Carrier Proteins; D011506:Proteins; D024341:Xanthophylls; C018494:crustacyanins; D019207:beta Carotene; C005904:BNPS-skatole; D002338:Carotenoids; D014364:Tryptophan; C005948:astaxanthine; D012862:Skatole