Transmembrane orientation and receptor-like structure of the Rhizobium meliloti common nodulation protein NodC

Abstract

The 46.8‐kd NodC protein of Rhizobium meliloti is a membrane protein, essential for nodule formation. Gene fusions of nodC to a portion of the λ cI repressor gene were used to define the membrane‐anchor domain which is necessary for membrane insertion of the NodC protein into the membrane. The transmembrane orientation of NodC was confirmed by surface‐specific radiolabeling and proteolysis experiments. A highly hydrophobic transmembrane‐anchor domain was found near the carboxyl terminus, separating a large extracellular domain which contains an unusual cysteine‐rich cluster from a short putative intracellular domain. Cross‐linking studies showed that the NodC protein exists in the membrane probably as a dimer. The domain structure of the NodC protein shows striking similiarities with cell surface receptors. In nodules of various legumes a truncated form of the NodC protein was detected. The processed NodC was associated with the bacteroids and the amount of this protein increased during nodule development.

The NodC protein of Azorhizobium caulinodans is an N-acetylglucosaminyltransferase.

“…Only for NodB has a function been shown; it is an enzyme that removes the N-acetyl moiety from the nonreducing end of N-acetylglucosamine oligosaccharides (10). The role of NodC is controversial, because it was reported to share sequence homology with chitin synthases (11)(12)(13) and to be an outer membrane protein with receptor structure (14)(15)(16). Finally, NodA has been proposed to be an acyltransferase (17).…”

Phylogeny of Sym plasmids of rhizobia by PCR-based sequencing of a nodC segment

“…The region amplified is a relatively variable part of the molecule and thus has a high density of information. The amino acid sequence deduced for this region is proposed to be an extracellular domain (9). The sequences of the amplification primers are as follows: 251F, AYGTIGTYGAYGAYGG WTC; 566R, AGCCARTACTCCATGTCGATCAA.…”

Genetic derepression of a developmentally regulated lipopolysaccharide antigen from Rhizobium leguminosarum 3841

“…The flavone-inducible nodC gene product has also been shown to be a membrane protein (24), and several other nod genes have DNA sequences that suggest a membrane location (38).…”