Re: [ccp4bb] Crystallizing a membrane associated protein

2010-08-01 Thread Daniel Bonsor
By size exclusion, it eluted where a 30kDa protein would be expected to elute. As for functional assay, I am currently trying to express its binding partner, though it shows a lot of degradation. But when I mix both proteins and run by size exclusion it causes the peaks of its binding partner to

Re: [ccp4bb] Crystallizing a membrane associated protein

2010-08-01 Thread Ho Leung Ng
Hi Dan, I agree with Bert's general approach. How does your purified protein look under size exclusion chromatography or DLS? Do you have a functional assay? ho

Re: [ccp4bb] Crystallizing a membrane associated protein

2010-08-01 Thread Daniel Bonsor
It behaves very well. No precipitation/cloudiness during purification. Secondary structure estimation by CD is ~50% alpha helical, 25% beta-sheet and 25% random coiled. I screened at 2, 4, 6 and 8mg/ml (8mg/ml around about 60:40% precipitation). If any other information is needed, just ask. Th

Re: [ccp4bb] Crystallizing a membrane associated protein

2010-08-01 Thread Van Den Berg, Bert
Hi Daniel, Whether or not I would introduce detergents would depend on the behavior of the protein during purification and crystallization. Does it behave well during purification in the absence of detergents? In your crystallization screens, do most of the drops have heavy precipitation? If th

[ccp4bb] Crystallizing a membrane associated protein

2010-08-01 Thread Daniel Bonsor
I have a 30kDa protein which I have been trying to crystallize. I have tried in the conventional way using Hampton screens but no luck so far. CD of the protein shows it is folded. However reading the literature I found out it is strongly associated with the inner membrane of H. pylori. This was