Some nodulin and Nod proteins show similarity to specific animal proteins

Abstract

During the development of a legume root nodule several genes encoding nodule-specific plant proteins (nodulins) are specifically activated (18). The nodulins can be divided into early and late nodulins. Early nodulins are primarily involved in development and progression of the infection (30,35), while the late nodulins are involved in nodule function. The functions of some of the late nodulins like leghemoglobin (1), uricase (4,24), nodule-specific glutamine synthase (3,7) and sucrose synthase (21,33) are known. However the function of the majority of the nodulins are at present unknown. The bacterial symbiotic partner encodes several proteins (Nod proteins) that are important for the formation of a functional nodule and for host specificity, but the biochemical functions of the Nod proteins are not known. Leghemoglobin is related to animal globins, and soybean uricase shows similarity to animal uricases (14,22). An indication of the function of some of the nodulin and Nod proteins can be found by searching the databases for similar proteins. In this paper we demonstrate similarity between nodulin 26 and several specific proteins. In addition we report a surprising similarity between the Rhizobium NodC protein and the Xenopus DG42 protein.