Adenylyltransferase involved in virulence by mediating the addition of adenosine 5'-monophosphate (AMP) to specific tyrosine residue of host Rho GTPases RhoA, Rac and Cdc42. The resulting AMPylation inactivates Rho GTPases, thereby inhibiting actin assembly in infected cells. Probably also acts as a cysteine protease, which may play a central role after invasion of host cell and in virulence. Possible member (with IbpB) of a 2 partner secretion. Probably able to bind bovine epithelial cells (host cells). May participate in the formation of fibrils at the surface of the bacteria. ATP + L-tyrosyl-[protein] = diphosphate + O-(5'-adenylyl)-L-tyrosyl-[protein] ATP + L-threonyl-[protein] = 3-O-(5'-adenylyl)-L-threonyl-[protein] + diphosphate Immunoglobulin-binding protein. High molecular weight-immunoglobulin binding protein IbpA, and probably other shorter forms. The fido domains mediate the adenylyltransferase activity. The arm region dictates the ability to recognize Rho family proteins. Leu-3668 and Lys-3670 probably lock the position of Tyr substrate in the correct orientation for modification (PubMed:20622875). When associated with Cdc42 target, adopts a conformation that mimicks the GDI-bound state of Rho GTPases. The long form of the protein is probably processed, and/or the transcript may be subject to differential translational initiation. The reaction mechanisms probably follows a substrate-assisted attack of ATP. According to this model, His-3717 acts by attracting a proton from the Tyr substrate, thereby preparing the Tyr as a nucleophile to attack the alpha-phosphate of ATP. This model is consistent with the observation that hydrolysis of ATP is very slow in the absence of Rho GTPases (PubMed:20622875). In the central section; belongs to the fic family. In the C-terminal section; belongs to the peptidase C58 family. Was originally [PubMed:8245839] thought to be a 76 kDa immunoglobulin-binding protein; it is now apparent that the gene is much longer but how it is translated and processed is unclear.