Fig 5.

SDS-PAGE of PhaM and PhaP5 after chemical cross-linking. Oligomerization of PhaP5-His₆ (A) and PhaM-His₆ (B) was analyzed using glutardialdehyde cross-linking as described in Materials and Methods. Cross-linking of PhaP5 led to decrease of the monomer band and to the formation of a dominant ∼30- to 34-kDa product, which corresponds to a dimer and to minor products of higher apparent molecular masses corresponding to tetra- to hexamers. Formation of PhaP5 dimers was also observed after heating (95°C, 10 min) of PhaP5-His₆ protein prior to cross-linking, but denaturation of PhaP5-His₆ by preincubation with 0.5% SDS prevented the formation of oligomers. When samples with PhaM-His₆ were subjected to cross-linking, the bands corresponding to monomers and to PhaM degradation products completely disappeared and high-molecular-weight products (HMW) with apparent molecular masses of >250 kDa were detected (B).