The goals are: (1) to explore and define the relationship of the cardiovirus genus to other members of the picornavirus family, and (2) to exploit unique features of the cardioviruses to examine fundamental questions about picornaviral translation, proteolytic processing and morphogenesis. One specific aim is to complete the identification of all enzymes involved in sequential proteolytic processing of the encephalomyocarditis (EMC) polyprotein. Cell-free synthesis, genetic engineering and site-specific mutagenesis techniques will be used to characterize viral protease 3C, a "second" viral protease (peptide 2A or 2B), and the maturation processing of capsid precursor peptide VPO. Enzyme specificities and cleavage site requirements will also be determined. The 5'on-coding region of EMC will be examined with the aim of characterizing the sequences and possible secondary structures which are necessary for efficient translation of polyprotein in cell-free systems. If possible, a full-length, infectious clone of EMC will be derived, and used to help define the biological role of the cardioviral poly C tract, and other 5' non-coding features. A third aim is derivation of the complete nucleotide sequences of two important cardiovirus strains: (1) mengovirus and (2) the diabetogenic varient of EMC, designated EMC-D. The EMC-D virus produces a pronounced diabetes-like syndrome in mice by infecting and destroying pancreatic beta cells. It has been exceptionally well characterized in vivo, and may serve as an animal virus model for insulin-dependent diabetes in man. A fourth aim is to compare and contrast available picornaviral sequence data (including those of the cardioviruses) by computer analysis to determine how and where the different viruses are analogous. The information will clarify interviral relationships in terms of genome organization, base compositions, codon frequencies, sequence-predicted antigenic differences, capsid structure (amino acid sequences vs. published crystallographic data) and possible phlogeny.