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Bacterial type IV secretion systems (T4SSs) are composed of two major subfamilies, conjugation machines dedicated to DNA transfer and effector translocators for protein transfer. We show here that the Escherichia coli pKM101-encoded conjugation system, coupled with chimeric substrate receptors, can be repurposed for transfer of heterologous effector proteins. The chimeric receptors were composed of the N-terminal transmembrane domain of pKM101-encoded TraJ fused to soluble domains of VirD4 homologs functioning in Agrobacterium tumefaciens, Anaplasma phagocytophilum, or Wolbachia pipientis. A chimeric receptor assembled from A. tumefaciens VirD4 (VirD4 At ) mediated transfer of a MOBQ plasmid (pML122) and A. tumefaciens effector proteins (VirE2, VirE3, and VirF) through the pKM101 transfer channel. Equivalent chimeric receptors assembled from the rickettsial VirD4 homologs similarly supported the transfer of known or candidate effectors from rickettsial species. These findings establish a proof of principle for use of the dedicated pKM101 conjugation channel, coupled with chimeric substrate receptors, to screen for translocation competency of protein effectors from recalcitrant species. Many T4SS receptors carry sequence-variable C-terminal domains (CTDs) with unknown function. While VirD4 At and the TraJ/VirD4 At chimera with their CTDs deleted supported pML122 transfer at wild-type levels, ⌬CTD variants supported transfer of protein substrates at strongly diminished or elevated levels. We were unable to detect binding of VirD4 At 's CTD to the VirE2 effector, although other VirD4 At domains bound this substrate in vitro. We propose that CTDs evolved to govern the dynamics of substrate presentation to the T4SS either through transient substrate contacts or by controlling substrate access to other receptor domains. IMPORTANCEBacterial type IV secretion systems (T4SSs) display striking versatility in their capacity to translocate DNA and protein substrates to prokaryotic and eukaryotic target cells. A hexameric ATPase, the type IV coupling protein (T4CP), functions as a substrate receptor for nearly all T4SSs. Here, we report that chimeric T4CPs mediate transfer of effector proteins through the Escherichia coli pKM101-encoded conjugation system. Studies with these repurposed conjugation systems established a role for acidic C-terminal domains of T4CPs in regulating substrate translocation. Our findings advance a mechanistic understanding of T4CP receptor activity and, further, support a model in which T4SS channels function as passive conduits for any DNA or protein substrates that successfully engage with and pass through the T4CP specificity checkpoint.T he type IV secretion systems (T4SSs) display striking versatility among the known bacterial translocation systems in their capacity to translocate DNA and protein substrates to bacterial or eukaryotic target cells (1, 2). Members of one major T4SS subfamily, the conjugation machines, mediate transfer of mobile DNA elements and are responsible for widespr...

1. An analysis of the original PTA deficient family, including coagulation studies performed upon 13 members comprising 4 generations, has been presented. 2. PTA deficiency is transmitted as an autosomal dominant trait with a probable high degree of penetrance and variable expression of the gene. 3. PTA deficiency can occur its varying degrees ranging from a severe form with prolonged clotting time and markedly abnormal heparin clotting time and prothrombin utilization to a mild form manifesting a normal clotting time and slightly impaired prothrombin utiliztition. 4. Studies on the treatment of PTA deficiency reveal that the defect is corrected by the administration of stored plasma with the effect gradually disappearing over the period of one week. 5. Various properties of PTA are discussed and compared with AHG and PTC.

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