. . . response: living with gravity.
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Biomedical subjects
Publications and source records attributed to S Ljung.
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In searching for novel peptides with affinity for cadmium, the phage display technique was utilized. In the selection procedure, cadmium ions were immobilized on a metal chelating Sepharose gel. The peptides selected from a hexapeptide library showed no homology to naturally occurring metallothioneins. From the phage clones selected in the biopanning process, phages with affinity for Cd-109 in free solution were identified. The peptide His-Ser-Gln-Lys-Val-Phe, which was found to exhibit the strongest relative affinity for Cd-109, was cloned into Escherichia coli as a fusion to the cell surface exposed area of the outer membrane protein OmpA. Escherichia coli cells expressing this peptide showed increased survival in growth media containing up to 1.2 mM CdCl2 when compared with cells not expressing this peptide on their surface.
To examine the role of the connecting region in the artificial bifunctional enzyme beta-galactosidase/galactose dehydrogenase, linkers of different length were inserted between the catalytic units. The specific activity of the galactose dehydrogenase part of the complex was increased when longer linkers (9 and 13 amino acids) were used as connectors. These bifunctional enzymes were predominantly found to comprise hexamers, however, complexes of higher molecular weight were also formed. The sequential reaction was carried out more efficiently when hybrid enzymes with the longer linkers were used as demonstrated both in vitro by using purified protein preparations as well as in vivo by determining the growth rates of recombinant E. coli cells on a minimal medium containing lactose.