Diversity in function and regulation of MAP kinase pathways.

Eukaryotic cells from yeast to humans use sequential protein kinase reactions to regulate complex cellular functions. Equivalent protein kinases in different pathways have significant sequence homologies; however, little crossover in phosphorylation of substrates between pathways normally occurs. Assembly of kinase complexes and discrimination of substrates provide the selectivity of sequential protein kinase pathways to regulate such diverse cellular functions as osmoregulation, cell-wall biosynthesis, growth and differentiation.