Members of a broadbean nodulin family with partial homologies to the alfalfa nodulin 25 are composed of two types of amino acid repeats flanked by unique amino acid sequence termini

authored by
Helge Küster, Andreas M. Perlick, Alfred Pühler
Abstract

Five cross-hybridizing cDNAs from clone group 'VfNDS-L' of a broadbean nodule-specific cDNA library differed by five specific in-frame deletions within the coding region. Northern blot analysis revealed that the transcripts represented by these clones were expressed in a nodule-specific way and therefore encoded a new family of broadbean nodulins. These nodulins have been designated Nvf-28/32. The Nvf-28/32 proteins were between 269 and 299 amino acids long with a high proportion of charged amino acids and contained a putative signal peptide of 20 amino acids. Sequence analysis indicated that the central part of the Nvf-28/32 proteins was composed of two different types of repeating amino acid stretches designated 'repeat 1' and 'repeat 2', whereas the N- and C-termini were unique. In contrast to 'repeat 1' stretches, which contained both positively and negatively charged amino acid residues, 'repeat 2' sequences did not contain any positively, but a total of 13 negatively charged amino acid residues. We could demonstrate that the five deletions identified exactly corresponded to complete repeats. The unique sequence termini of the Nvf-28/32 proteins displayed strong homologies to the late nodulin 25 from alfalfa. In addition, the repeating units identified were significantly homologous to several, but not all exon parts of this protein. We speculate that the 'VfNDS-L' transcripts were derived from a differential splicing mechanism and that the Nvf-28/32 proteins fulfil a structural rather than an enzymatic function within the broadbean root nodule.

External Organisation(s)
Bielefeld University
Type
Article
Journal
Plant molecular biology
Volume
24
Pages
143-157
No. of pages
15
ISSN
0167-4412
Publication date
01.01.1994
Publication status
Published
Peer reviewed
Yes
ASJC Scopus subject areas
Agronomy and Crop Science, Genetics, Plant Science
Electronic version(s)
https://doi.org/10.1007/BF00040581 (Access: Unknown)