Two polymorphs of an independent amyloid core in medin's C-terminal region.

Medin 31–53 (medin C-APR) forms two coexisting amyloid polymorphs with cryo-EM–measured spacings of 2.71 and 2.91 Å, matching full-length medin’s aggregation lag time.

• Why it matters: The C-terminal region is predicted to be strongly amyloidogenic, but it was unclear whether it can aggregate independently and how its structure relates to full-length medin fibrils.
• What they did: The isolated medin C-APR was tested for aggregation and then structurally characterized by cryo-EM, revealing two polymorphs built from the same two-stranded beta-arch and pseudo-21 protofilament pair.
• The result: The two polymorphs differ only in how many accessory chains recruit to the exposed hydrophobic face, implying the medin C-terminus carries an amyloid core distinct from the full-length fibril.

AI summary of the abstract · may contain errors · not medical advice · read the paper.