Find iron in a protein

How can an iron atom be part of a protein assembly?

Locate heme iron and distinguish an experimental structure record from an illustrative representation.

An iron site in hemoglobin sits within a heme group, which is held by the surrounding protein. Select the protein, then the heme, then iron. These connected levels explain why the element's environment matters. An iron atom in this setting does not behave like a loose piece of metal.

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EXPLORE THE MODEL

Inspect deposited hemoglobin structures

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Cα traces, heme atoms and O₂ from deposited structures; biological assembly operators applied. Missing atoms remain missing. No morph or measured trajectory is asserted.

Deposited state

Representation

View angle20 °

StructureDeoxy · 1A3N

RepresentationProtein and hemes

SourceDeposited X-ray structure

Compare two separately measured structures. Their different preparation and resolution mean this is not a controlled movie of oxygen binding.

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HOW DO WE KNOW?

Evidence & limits

Deposited structure + original rendering

What this interaction establishes

Locate heme iron and distinguish an experimental structure record from an illustrative representation.

Cα traces, heme atoms and O₂ from deposited structures; biological assembly operators applied. Missing atoms remain missing. No morph or measured trajectory is asserted.

Source bindings for this explanation

Start here

Sources: S08, S09, S12, SRC-1HHO.

Explore the science

The reference entry 1A3N describes deoxy human hemoglobin. Its biological assembly 1 contains two alpha and two beta chains, with heme groups supplying the iron sites. The deposited model was determined using X-ray diffraction at 1.80 Å resolution. Those metadata belong to that entry; they must not be transferred to an unrelated drawing or a predicted structure. A schematic heme locator is an educational guide, while deposited coordinates retain their own provenance.

Sources: S08, S09, S12, SRC-1HHO.

Go deeper

A structure record includes experimental method, assembly, ligands, modeled residues, validation information and revision history. The inspected 1A3N entry is version 1.4, revised on 12 August 2026. Its reported modeled residue count differs from the deposited sequence count, illustrating why absent coordinates must not be silently invented. Selecting a site makes the coordinate model inspectable; it does not prove that every atom in a living molecule is fixed at the displayed location under every condition.

Sources: S08, S09, S12, SRC-1HHO.

Limitations

1A3N is deoxygenated; it does not supply bound O₂ coordinates for an oxygenated story. A schematic locator must be labeled separately from deposited atomic coordinates. The reference structure is not a complete movie of a living protein or a personal health measurement.

Sources: S08, S09, S12, SRC-1HHO.

Keep these boundaries in mind

1A3N is deoxygenated; it does not supply bound O₂ coordinates for an oxygenated story.
A schematic locator must be labeled separately from deposited atomic coordinates.
The reference structure is not a complete movie of a living protein or a personal health measurement.

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Scientific explanations with linked references. Model calculations retain their stated assumptions and limits.

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recognition

Where is the selected iron site located?

Within a heme group associated with the proteinAs the entire outer cell membraneAs an independent metal nail inside the protein

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mechanism

Why inspect the heme and nearby protein along with iron?

Only an atom’s name can affect behaviorThe local molecular environment helps determine functionThe protein changes iron’s proton count with each interaction

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evidence

Which description accurately identifies reference entry 1A3N?

An oxygenated structure generated by this animationA live microscope film of blood flowA deoxygenated human hemoglobin coordinate model determined by X-ray diffraction

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transfer

A protein entry lacks coordinates for a short sequence region. What should a learning viewer do?

Make the absence explicit and label any separate reconstructionInvent coordinates and label them experimentalErase the whole protein’s provenance

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Find the relevant scale Next: Compare binding states

EXPLORE THE MODEL

Inspect deposited hemoglobin structures

INTERACTIVE 3D744 visible sites

1A3N · hemoglobin in three dimensionsDrag to rotate · scroll or pinch to zoom

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Inspect

Four folded protein chains position four iron-containing hemes. Rotate the deposited coordinate model, then isolate a heme to examine the local environment.

What this representation means

RCSB PDB 1A3N, X-ray resolution 1.80 Å. Selected deposited coordinates and biological assembly operators; atom display sizes are exaggerated. Cα connectors indicate sequence continuity, not direct Cα–Cα bonds. Heme connectors use a distance heuristic, not a bond-order assignment. Missing residues are not reconstructed. Oxy/deoxy views are separately centered, not aligned or morphed.

Coordinate record: 1A3N
Experimental resolution: 1.80 Å
Assembly: Four chains · biological tetramer
Oxygen state: No OXY ligand deposited

Source: www.rcsb.org ↗

Deposited record 1A3N · revision 1.4, 2026-08-12. Archive coordinates: CC0. Original rendering.

Loading deposited structure data…

Cα traces, heme atoms and O₂ from deposited structures; biological assembly operators applied. Missing atoms remain missing. No morph or measured trajectory is asserted.

Deposited state

Representation

View angle20 °

StructureDeoxy · 1A3N

RepresentationProtein and hemes

SourceDeposited X-ray structure

Compare two separately measured structures. Their different preparation and resolution mean this is not a controlled movie of oxygen binding.

INTERACTIVE 3D744 visible sites

1A3N · hemoglobin in three dimensionsDrag to rotate · scroll or pinch to zoom

Turn slowlyConnectionsFocus

Inspect

Four folded protein chains position four iron-containing hemes. Rotate the deposited coordinate model, then isolate a heme to examine the local environment.

What this representation means

Coordinate record: 1A3N
Experimental resolution: 1.80 Å
Assembly: Four chains · biological tetramer
Oxygen state: No OXY ligand deposited

Source: www.rcsb.org ↗

Deposited record 1A3N · revision 1.4, 2026-08-12. Archive coordinates: CC0. Original rendering.