Figure 4: Confirmation of protein interactions and immunostaining with a PXL-1 antibody (A). Screening by the yeast two-hybrid method of a collection of 30 known components of dense bodies and M-lines revealed that the six indicated proteins interact with PXL-1. By domain mapping, the LD motif region is sufficient for interaction with DEB-1 (vinculin) and LIM-8, and the LIM domain region is sufficient for interaction with UNC-95 and UIG-1 (a Cdc42 GEF). UNC-96 and HUM-6 are also able to bind to PXL-1. (B) These interactions, except that with HUM-6, were verified using purified proteins. Yeast-expressed HA-tagged PXL-1 was precipitated with anti-HA beads, washed, incubated with bacterially expressed MBP of the indicated MBP fusion proteins, and washed, and the eluted proteins were separated on a gel, blotted, and reacted with either anti-MBP or anti-HA. All tested proteins except UNC-96 showed conclusive results, with a faint band observed in 5B when reacted with anti-MBP. A paxillin (PXL-1) polyclonal rabbit antibody was produced to detect PXL-1 in C. elegans as well as in yeast expressing HA-PXL-1. PAT-3/β-integrin (GFP; Ci) is a major component of dense bodies, M-lines, and attachment plaques, and the PXL-1 antibody (Cii) clearly colocalizes with PAT-3/&
sup2;-integrin in dense bodies and adhesion plaques (Ciii). The PXL-1 antibody also stains M-lines, but very weakly (not shown). Paxillin from the nematode lysate displays a slower mobility than that of nematode paxillin expressed in yeast (see Discussion) (D). Bar, 2 μm.