ISB Ca2+ATPase Project Home Page

PDB ID "1EUL"

George Lee

The "Ca2+ATPase" protein, Sarcoplasmic/endoplasmic reticulum calcium ATPase 1, is a Calcium Ion Pump from the skeletal fast twitch muscle of Oryctolagus Cuniculus (rabbilt).

The P-type ATPases use the chemical energy from ATP to transport ions across the membrane against a concentration gradient. In skeletal muscle, the Calcium ATPase pumps calcium irons released in muscle cells during contraction, from the cytoplasm back into the sarcoplasmic reticulum. This intracellular process causes muscle cells to relax after cytosolic calcium increases during excitation. The Ca²⁺ ATPase (EC 3.6.3.8) that carries out this pumping is a representative member of the P-type ATPase enzymes group. Among the other P-type ion-transporting ATPases subfamilies such as Na⁺K⁺ ATPase and gastric H⁺K⁺ ATPase, the Ca²⁺ ATPase from skeletal muscle sarcoplasmic reticulum is structurally and functionally the best-studied member known today.

Secondary Structure Assignment

The cytoplasmic headpiece has a split appearance consisting of three separated domains A, N and P.

The phosphorylation site is located in domain P, and the adenosine moiety of nucleotide is bound to domain N.

The transmembrane region comprises 10 a-helices. The length of helices and the inclination to the membrane vary substantially.

The domain P at the central part of the structure is composed of the N-terminal and C-terminal two parts which are widely separated in the amino-acid sequence. These two parts are assembled into 7b-strands and eight short associated helices.

http://biobase.dk/~axe/structure.html

SCOP Results

Root	scop
Class	Membrane and cell surface proteins and peptides	Does not include proteins in the immune system
Fold	Membrane all-alpha
Superfamily	Membrane all-alpha	This is not a true superfamily family; in this provisional classification each transmembrane helix is considered to be a 'domain'
Family	Calcium ATPase
Protein	Calcium ATPase

Provisional classification- cytoplasmic domains will be cut out and classified in future release the catalytic domain belongs to the HAD-like suprfamily (e.g. the catalytic domain of L-2-Haloacid dehalogenase 1QQ5)

Three PDB Entry Domains were found in the same Superfamily of classification.

1eul: complexed with ca
chain a

1iwo: Structure in the absence of calcium ions complexed with tg1
chain a
chain b

1kju: Structure in the e2 state
chain a

CATH Results

The Classification of "1EUL" belongs to the Hydrolase Sequence family (3.40.50.1000.2):

Class	Alpha Beta	3
Architecture	3-Layer(aba) Sandwich	40
Topology(fold family)	Rossmann fold	50
Homologous Supperfamily	Dehalogenase	1000
Sequence family	Hydrolase	2

The Domain was identified as :

1EULA4

No fold relatives were found.  Either no other non-identical relatives within this fold group or the structural comparisons for this domain have not yet been calculated.

Crystallography Summary

3-D Microrystals (<20mm thickness) was formed at pH6.1 in the presence of 10 millimolar C ²⁺ (in buffered CaCl₂ solution) with an exogenous lipid specimen prepared from rabbit hind leg muscle.

Exp. Method	X-ray Diffraction
Data Collection	Spring-8
Structure Determination	MIRAS.
Resolution	2.60Å.
R-factor	0.250.
R-free	0.307.
Unit Cell Dimension	a =166.07 Å, b =64.31 Å, c =147.02 Å
Unit Cell Angles	a =90.00°, b =98.0°
Polymer Chains	A
Residues	994 amino acid
Atoms	7673

CE Combinatorial Extension Conclusion

The ViusalFasta result shown the scores of the comparison between 1EUL:A and 1IWO:A as follows:

Sequence Comparision Between 1EUL.pdb and 1IWO.pdb:

Structure Comparision Between 1eul (E1-Ca2)+ and 1iwo (E2-TG):

Alignment and Ligands

References

• FUNCTION: THIS MAGNESIUM DEPENDENT ENZYME CATALYZES THE HYDROLYSIS OF ATP COUPLED WITH THE TRANSLOCATION OF CALCIUM FROM THE CYTOSOL TO THE SARCOPLASMIC RETICULUM LUMEN. CONTRIBUTES TO CALCIUM SEQUESTRATION INVOLVED IN MUSCULAR EXCITATION/CONTRACTION (BY SIMILARITY).
• CATALYTIC ACTIVITY: ATP + H₂O + Ca²⁺(Cis) = ADP + phosphate + Ca²⁺(Trans).
• ENZYME REGULATION: REVERSIBLY INHIBITED BY PHOSPHOLAMBAN (PLN) AT LOW CALCIUM CONCENTRATIONS. DEPHOSPHORYLATED PLN DECREASES THE APPARENT AFFINITY OF THE ATPASE FOR CALCIUM. THIS INHIBITION IS REGULATED BY THE PHOSPHORYLATION OF PLN.
• SUBUNIT: ASSOCIATED WITH SARCOLIPIN (SLN) (BY SIMILARITY) AND PHOSPHOLAMBAN (PLN).
• SUBCELLULAR LOCATION: INTEGRAL MEMBRANE PROTEIN. SARCOPLASMIC AND ENDOPLASMIC RETICULUM.
• ALTERNATIVE PRODUCTS:
• Alternative splicing [2 named forms]

Name	SERCA1B
Synonyms	Neonatal
Isoform ID	P04191-1
This is the isoform sequence displayed in this entry.

Name	SERCA1A
Synonyms	Adult
Isoform ID	P04191-2
Features which should be applied to build the isoform sequence: VSP_000356.

• TISSUE SPECIFICITY: SKELETAL MUSCLE, FAST TWITCH MUSCLE (TYPE II) FIBERS.
• DEVELOPMENTAL STAGE: ISOFORM SERCA1A IS PREDOMINANTLY FOUND IN ADULT AND ISOFORM SERCA1B IN NEONATAL SKELETAL MUSCLE.

Abstract of Citation

PDB Information