Research Articles
Tobacco cytochrome
b
5: cDNA isolation, expression analysis and
in vitro protein targeting
Mark A. Smith1, A. Keith Stobart1, Peter R. Shewry2 and Johnathan A. Napier2
| (1) | Department of Botany, University of Bristol, BS8 1UG Bristol, UK |
| (2) | Department of Agricultural Sciences, University of Bristol, Institute of Arable Crops Research, Long Ashton Research Station, Bristol, BS18 9AF, UK |
Received: 3 December 1994 Accepted: 5 April 1994
Abstract A full-length clone encoding cytochrome
b
5 has been isolated from a tobacco leaf cDNA library in
gt11 by PCR using degenerate primers. This cDNA encodes a protein of 139 residues which exhibits a high degree of homology to other cytochrome
b
5s, the message for which is expressed predominantly in developing seeds and in pigmented flower tissue. In the developing tobacco seed the mRNA is abundant at very early stages (<10 days after flowering). Southern analysis indicated that more than one gene encodes cytochrome
b
5 in the tobacco genome.
In vitro transcription and translation studies of the cDNA indicated that the protein inserts into the ER membrane by a non-SRP-mediated pathway and that the
C-terminus of the protein is required for targeting and insertion.
Key words cytochromeb
5
- seed development - oil seeds - microsomal targeting - mRNA expression
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