Fig. 4.
Proposed model of the mid-sized A-IM/A-IM double belt is compatible with the K40-K239 cross-link. In the midsized belt, the polypeptide chain in each molecule is shown bent back around G39 (A). The two belt-forming molecules are related via the two-fold (B). Yellow highlight shows chemical cross-link K40-K239 that was found on the large ∼12 nm rHDL(A-IM/A-IM) and is compatible with the midsized belt conformation (10). Bar size shows the upper limit for the Cα-Cα distance (26 Å) that can be cross-linked by BS3 (10).