In an alpha-helix
, the protein chain is coiled like a loosely-coiled spring.
The available X-ray crystallographic structure of PA complex with PB1 N-terminal fragment (amino acids 1-15) shows that, when bound to PA1, the secondary structure of 115 N-terminal fragment of PB1 is an alpha-helix
In the Style/Edit Global Style menu, uncheck "alpha-helix
"; the cylinders disappear.
There are two types of arrangement for secondary structures: the alpha-helix
and beta sheets.
In one case, that of a glucocorticoid receptor protein, they found a specific spiral structure -- an alpha-helix
-- that appears to spur transcription.
Studying the configuration of how calpastatin bound to the active site of the calpain complex, "we found that there was a small alpha-helix
that fit into the active site of the calpain enzyme," Greenbaum said.
Whereas a single alpha-helix
consists of an elegant spiral of 15 to 20 amino acids, the beta sheet requires 60 to 70 amino acids.