Subunit composition and in vivo substrate-binding characteristics of Escherichia coli Tat protein complexes expressed at native levels

Abstract

The Tat system transports folded proteins across the bacterial cytoplasmic membrane and the thylakoid membrane of plant chloroplasts. Substrates are targeted to the Tat pathway by signal peptides containing a pair of consecutive arginine residues. The membrane proteins TatA, TatB and TatC are the essential components of this pathway in Escherichia coli. The complexes that these proteins form at native levels of expression have been investigated by the use of affinity tag-coding sequences fused to chromosomal tat genes. Distinct TatA and TatBC complexes were identified using size-exclusion chromatography and shown to have apparent molecular masses of ∼700 and 500 kDa, respectively. Following ..