Complex sentence: The expression host of choice for the expression of many proteins is "Escherichia coli" as the production of heterologous protein in "E. coli" is relatively simple and convenient, as well as being rapid and cheap.
Split into simpler sentences: The expression host of choice for the expression of many proteins is "Escherichia coli". Protein expression in "E. coli" is relatively simple and convenient, as well as being rapid and cheap.