A CONSERVED BURP DOMAIN DEFINES A NOVEL GROUP OF PLANT-PROTEINS WITH UNUSUAL PRIMARY STRUCTURES

We have identified a new class of plant proteins containing a common C -terminal region, which we have termed the BURP domain. These proteins are defined not only by the BURP domain, but also by the overall simi larity in their modular construction. The BURP domain proteins consist of either three or four modules: (i) an N-terminal hydrophobic domain - a presumptive transit peptide, joined to (ii) a short conserved seg ment or other short segment, (iii) an optional segment consisting of r epeated units which is unique to each member, and (iv) the C-terminal BURP domain. These individual modules appear to be combined to form tw o main classes of BURP domain proteins. The BURP domain proteins, desp ite the similarities in their primary structural features, show no obv ious similarities in the tissues or conditions under which they are ex pressed. The presence of the conserved BURP domain in diverse plant pr oteins suggests an important and fundamental functional role for this domain.