Rasal is a modular multi-domain protein of the GTPase-activating protein 1 (GAP1) family; its four known members, GAP1m, Rasal, GAP1IP4BP and Capri, have a Ras GTPase-activating domain (RasGAP). This domain supports the intrinsically slow GTPase activity of Ras by actively participating in the catalytic reaction. In the case of Rasal, GAP1IP4BP and Capri, their remaining domains are responsible for converting the RasGAP domains into dual Ras- and Rap-GAPs, via an incompletely understood mechanism. Although Rap proteins are small GTPase homologues of Ras, their catalytic residues are distinct, which reinforces the importance of determining the structure of full-length GAP1 family proteins. To date, these proteins have not been crystallized, and their size is not adequate for nuclear magnetic resonance (NMR) or for high-resolution cryo-electron microscopy (cryoEM). Here we present the low resolution structure of full-length Rasal, obtained by negative staining electron microscopy, which allows us to propose a model of its domain topology. These results help to understand the role of the different domains in controlling the dual GAP activity of GAP1 family proteins.
This study determined the immunoglobulin (A and G) activity against gastrointestinal nematodes (GIN) and also the hematological parameters in four beef-calf breeds naturally infected in a tropical region of Mexico. Thirty-six infected calves were used to determine the fecal nematode egg counts (FEC), the IgA and IgG activity in serum and saliva, the packed cell volume (PCV), the plasmatic protein (PP) and the differential leukocyte counts. These parameters were measured for a five-month period. ELISA assay was performed using adult worm crude antigen (AWCA) from Haemonchus contortus, Trichostrongylus colubriformis, Mecistocirrus digitatus and Cooperia punctata. The variables were analyzed using a fixed model according to the breed group. The FEC records (means ± standard deviation) for the different breeds were: Brangus (122±115), Charolais (391±507), Guzerat (294±326) and Brown Swiss (413±395). No statistical differences (P>0.05) were found among breeds. Cooperia and Haemonchus were the main identified genera in the coprocultures. Differences in hematological parameters were observed among breeds (P<0.01); Guzerat showed the highest PCV (42.6±4.7%). The lowest leukocyte counts were observed in the Charolais breed (9.2±2.4 × 109 cells L-1). Differences between Guzerat and Charolais were only detected in eosinophils, neutrophils and lymphocytes. Increased activity of IgA was observed against M. digitatus (21% OD) compared with the response against C. punctata in serum samples (13% OD). The lowest IgA activity in serum and saliva was found in Guzerat calves. Charolais and Brown Swiss showed the highest IgA activity in serum and the highest value in saliva was found in Brangus.