Sequential and structural homology between intracellular pathogenesis-related proteins and a group of latex proteins

The intracellular pathogenesis-related proteins have been identified in a b road range of flowering plants. Some display quite different patterns of ex pression, in many cases unrelated to the pathogenic response. Nevertheless, these proteins are all very similar and in most cases share more than 35% sequence identity. In this report we investigate the significance of a rath er weak similarity between the intracellular pathogenesis-related (IPR or P R-10) proteins and a group of proteins identified in the latex of opium pop py and in Arabidopsis, among others. A sequence analysis held together with the recently published three-dimensional structure of Bet v 1, an IPR prot ein from birch pollen, strongly suggests sequential and structural homology between the two protein families.