Annotations: 6DBS

Domain Annotation: ECOD Classification ECOD Database Homepage

Chains	Family Name	Domain Identifier	Architecture	Possible Homology	Homology	Topology	Family	Provenance Source (Version)
B [auth C]	UNK_F_TYPE	e6dbsC2	A: beta sandwiches	X: Immunoglobulin-like beta-sandwich	H: Immunoglobulin-related	T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like	F: UNK_F_TYPE	ECOD (1.6)
B [auth C]	UNK_F_TYPE	e6dbsC1	A: beta complex topology	X: Domain II of HAP2 (From Topology)	H: Domain II of HAP2 (From Topology)	T: Domain II of HAP2	F: UNK_F_TYPE	ECOD (1.6)
A	UNK_F_TYPE	e6dbsA2	A: beta sandwiches	X: Immunoglobulin-like beta-sandwich	H: Immunoglobulin-related	T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like	F: UNK_F_TYPE	ECOD (1.6)
A	UNK_F_TYPE	e6dbsA1	A: beta complex topology	X: Domain II of HAP2 (From Topology)	H: Domain II of HAP2 (From Topology)	T: Domain II of HAP2	F: UNK_F_TYPE	ECOD (1.6)
C [auth B]	UNK_F_TYPE	e6dbsB2	A: beta sandwiches	X: Immunoglobulin-like beta-sandwich	H: Immunoglobulin-related	T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like	F: UNK_F_TYPE	ECOD (1.6)
C [auth B]	UNK_F_TYPE	e6dbsB1	A: beta complex topology	X: Domain II of HAP2 (From Topology)	H: Domain II of HAP2 (From Topology)	T: Domain II of HAP2	F: UNK_F_TYPE	ECOD (1.6)

Protein Family Annotation Pfam Database Homepage

Chains	Accession	Name	Description	Comments	Source
A, B [auth C], C [auth B]	PF10699	Male gamete fusion factor (HAP2-GCS1)	Male gamete fusion factor	The gene encoding Arabidopsis HAP2 is allelic with GCS1 (Generative cell-specific protein 1). HAP2 is expressed only in the haploid sperm and is required for efficient guidance of the pollen tube to the ovules. In Arabidopsis the protein is a predict ...	The gene encoding Arabidopsis HAP2 is allelic with GCS1 (Generative cell-specific protein 1). HAP2 is expressed only in the haploid sperm and is required for efficient guidance of the pollen tube to the ovules. In Arabidopsis the protein is a predicted membrane protein with an N-terminal secretion signal, a single transmembrane domain and a C-terminal histidine-rich domain [1]. HAP2-GCS1 is found from plants to lower eukaryotes and is necessary for the fusion of the gametes in fertilisation. Studies in the green alga Chlamydomonas and the malaria organism Plasmodium showed that it is involved in a novel mechanism for gamete fusion where a first species-specific protein binds male and female gamete membranes together after which a second, broadly conserved protein, either directly or indirectly, causes fusion of the two membranes together. The broadly conserved protein is represented by this HAP2-GCS1 domain, conserved from plants to lower eukaryotes [2]. In Plasmodium berghei the protein is expressed only in male gametocytes and gametes, having a male-specific function during the interaction with female gametes, and being indispensable for parasite fertilisation. The gene in plants and eukaryotes might well have originated from acquisition of plastids from red algae [3].	Domain

Gene Ontology: Gene Product Annotation Gene Ontology Database Homepage

Chains	Polymer	Molecular Function	Biological Process	Cellular Component
A, B [auth C], C [auth B]	Hapless 2	binding lipid binding	membrane organization protein localization cellular localization establishment of protein localization establishment of protein localization to membrane localization within membrane protein localization to membrane establishment of localization cellular component organization localization cellular macromolecule localization macromolecule localization cellular process cellular component organization or biogenesis membrane organization protein localization cellular localization establishment of protein localization establishment of protein localization to membrane localization within membrane protein localization to membrane establishment of localization cellular component organization localization cellular macromolecule localization macromolecule localization cellular process cellular component organization or biogenesis protein insertion into membrane sexual reproduction membrane fusion reproductive process plasma membrane fusion fertilization multicellular organismal reproductive process cellular process involved in reproduction in multicellular organism fusion of sperm to egg plasma membrane involved in single fertilization plasma membrane organization endomembrane system organization single fertilization	membrane-bounded organelle intracellular anatomical structure membrane intracellular vesicle cellular anatomical entity intracellular membrane-bounded organelle intracellular organelle cytoplasmic vesicle membrane vesicle membrane cytoplasmic vesicle organelle cytoplasm vesicle organelle membrane membrane-bounded organelle intracellular anatomical structure membrane intracellular vesicle cellular anatomical entity intracellular membrane-bounded organelle intracellular organelle cytoplasmic vesicle membrane vesicle membrane cytoplasmic vesicle organelle cytoplasm vesicle organelle membrane cell periphery plasma membrane cell projection plasma membrane region cell projection membrane plasma membrane bounded cell projection

InterPro: Protein Family Classification InterPro Database Homepage

Chains	Accession	Name	Type
A, B [auth C], C [auth B]	IPR040326	HAP2/GCS1	Family
A, B [auth C], C [auth B]	IPR018928	Generative cell specific-1/HAP2 domain	Domain

RCSB PDB Core Operations are funded by the National Science Foundation (DBI-1832184), the US Department of Energy (DE-SC0019749), and the National Cancer Institute, National Institute of Allergy and Infectious Diseases, and National Institute of General Medical Sciences of the National Institutes of Health under grant R01GM133198.