This project is concerned with the study of certain enzymes and other proteins that consist of multiple subunits and that assemble into macromolecular functional units. The glutamate dehydrogenases of vertebrates and of Neurospora crassa are enzymes of diverse properties that are regulated in different ways - the vertebrate ones by allosteric effectors, such as purine nucleoside di- and triphosphates, and those of Neurospora by the level of glutamate in the culture medium. The phycobiliproteins are obtained from algal organelles (phycobilisomes) that can be reassembled in vitro. We will continue to collaborate with A.N. Glazer (Univ. of California, Berkeley) and R.M. Sweet (UCLA Dept. of Chemistry) with the ultimate goal of obtaining the complete primary structures and conformations of these organelles and the mechanisms involved in their assembly. We will continue to study with H.G. Martinson (UCLA Dept. of Chemistry) interhistone contacts in nucleosomes as deduced by "zero-length" crosslinking studies. Such a contact point has been identified between histones 2A and 2B and will be more precisely defined. Studies on other sites of interaction are in progress. Covalent modifications of histones (introduced chemically or enzymically) and their effects on nucleosome structure and function will continue with particular emphasis on phosphorylation and the kinases involved in this post-translational modification.