<Tr> <Th_colspan="2"> T4SS </Th> </Tr> <Tr> <Td_colspan="2"> crystal structure of trac </Td> </Tr> <Tr> <Th_colspan="2"> Identifiers </Th> </Tr> <Tr> <Th> Symbol </Th> <Td> T4SS </Td> </Tr>

Compare and contrast constitutive secretion and regulated secretion