Tuna cytochrome c at 2.0 A resolution. II. Ferrocytochrome structure analysis

Area of Science:

• Biochemistry
• Structural Biology
• X-ray Crystallography

Background:

• Cytochromes c are vital electron transport proteins.
• Understanding their structure is key to cellular respiration.
• Previous studies established the structure of tuna ferricytochrome c.

Purpose of the Study:

• To determine the high-resolution X-ray crystal structure of tuna ferrocytochrome c.
• To investigate potential structural differences between ferrocytochrome c and ferricytochrome c.
• To analyze the role of invariant glycine residues in protein folding and stability.

Main Methods:

• X-ray crystal structure analysis
• Extended resolution analysis to 2.0 A
• Difference map studies

Main Results:

• The overall folding of tuna ferrocytochrome c is unchanged compared to ferricytochrome c.
• No significant structural differences were observed between the oxidized and reduced states.
• Six type II beta or 310 bends with obligatory glycines were identified, explaining 6 invariant glycines.

Conclusions:

• The oxidation state does not induce significant conformational changes in tuna cytochrome c.
• Invariant glycine residues are crucial for specific structural motifs (bends) and close packing in the protein.
• The precise role of one invariant glycine remains to be elucidated.