The C-terminus hot spot region helps in the fibril formation of bacteriophage-associated hyaluronate lyase (HylP2)

The bacteriophage encoded hyaluronate lyases (HylP and HylP2) degrade hyaluronan and other glycosaminoglycans. HylP2 forms a functional fibril under acidic conditions in which its N-terminus is proposed to form the fibrillar core, leading to nucleation and acceleration of fibril formation. Here we report the presence of a hot spot region (A 144 GVVVY 149) towards the carboxy terminus of HylP2, essential for the acceleration of fibril formation. The hot spot is observed to be inherently mutated for valines (A 178 AMVMY 183) in case of HylP. The N- terminal swapped chimeras between these phage HLs (N HylP 2 C HylP and N HylP C HylP2) or HylP did not form fibrils at acidic pH. However, seeding of prefibrils of HylP2 recompensed nucleation and led to fibrillation in N HylP C HylP2. The V147A mutation in the hot spot region abolished fibril formation in HylP2. The M179V and M181V double mutations in the hot spot region of HylP led to fibrillation with the seeding of prefibrils. It appears that fibrillation in HylP2 even though is initiated by the N-terminus, is accelerated by the conserved hot spot region in the C-terminus. A collagenous (Gly-X-Y) 10 motif in the N-terminus and a mutated hot spot region in the C-terminus of HylP affect fibrillar nucleation and acceleration respectively.