Seroatlas · Human Serome Atlas

SPACA1

Sperm acrosome membrane-associated protein 1

Also known as: SACA1_HUMAN, SAMP32

Cross-references: UniProt · Ensembl · Human Protein Atlas · GeneCards · NCBI Gene

Protein identityUniProt · HPA

UniProt accession
Q9HBV2
Gene
SPACA1
Ensembl
ENSG00000118434
Chromosome
6
Canonical length
294 aa
Protein class
Predicted membrane proteins
Subcellular location
Acrosome

OverviewNCBI Gene

The correlation of anti-sperm antibodies with cases of unexplained infertility implicates a role for these antibodies in blocking fertilization. Improved diagnosis and treatment of immunologic infertility, as well as identification of proteins for targeted contraception, are dependent on the identification and characterization of relevant sperm antigens. The protein expressed by this gene is recognized by anti-sperm antibodies from infertile males. Furthermore, antibodies generated against the recombinant protein block in vitro fertilization. This protein localizes to the acrosomal membrane of spermatids and mature spermatozoa where it is thought to play a role in acrosomal morphogenesis and in sperm-egg binding and fusion, respectively. [provided by RefSeq, Jul 2008]

Canonical amino-acid sequenceUniProt

294 residues, UniProt reviewed canonical sequence.

>Q9HBV2|SPACA1
     1  MSPRGTGCSA GLLMTVGWLL LAGLQSARGT NVTAAVQDAG LAHEGEGEEE TENNDSETAE
    61  NYAPPETEDV SNRNVVKEVE FGMCTVTCGI GVREVILTNG CPGGESKCVV RVEECRGPTD
   121  CGWGKPISES LESVRLACIH TSPLNRFKYM WKLLRQDQQS IILVNDSAIL EVRKESHPLA
   181  FECDTLDNNE IVATIKFTVY TSSELQMRRS SLPATDAALI FVLTIGVIIC VFIIFLLIFI
   241  IINWAAVKAF WGAKASTPEV QSEQSSVRYK DSTSLDQLPT EMPGEDDALS EWNE

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against SPACA1 can act on the native protein depends on physical access: surface and secreted proteins are reachable by circulating antibodies, intracellular proteins usually are not.

Antibody reachability
Intracellular
Secreted
No
Transmembrane segments
1
Mean surface accessibility (rSASA)
0.51
Highest tissue expression
40 nTPM

Expression across tissuesHPA

Tissue

  • testis: 40 nTPM
  • adipose tissue: 0 nTPM
  • adrenal gland: 0 nTPM
  • amygdala: 0 nTPM
  • appendix: 0 nTPM
  • basal ganglia: 0 nTPM

Single-cell type

  • early spermatids: 1,083 nCPM
  • late primary spermatocytes: 661 nCPM
  • late spermatids: 55 nCPM
  • early primary spermatocytes: 12 nCPM
  • sertoli cells: 5.7 nCPM
  • distal convoluted tubule cells: 3.5 nCPM

Immune cell

  • basophil: 0 nTPM
  • classical monocyte: 0 nTPM
  • eosinophil: 0 nTPM
  • gdT-cell: 0 nTPM
  • intermediate monocyte: 0 nTPM
  • MAIT T-cell: 0 nTPM

Brain region

  • hypothalamus: 0.2 nTPM
  • amygdala: 0.1 nTPM
  • basal ganglia: 0.1 nTPM
  • cerebral cortex: 0.1 nTPM
  • hippocampal formation: 0.1 nTPM
  • cerebellum: 0 nTPM

DiseaseUniProt · ClinVar · IEDB · PubMed

Four sources answering four different questions about SPACA1.

Disease | AllUniProt

Conditions SPACA1 is implicated in, by any mechanism.

Disease | GeneticClinVar

1 pathogenic / likely-pathogenic of 55 ClinVar records.

Conditions with pathogenic or likely-pathogenic variants.

  • Spermatogenic failure 85

Genetic constraint and essentialitygnomAD · DepMap

Does the body need this protein intact? Low LOEUF or a strong DepMap dependency means loss or blockade of the protein is likely to be felt.

gnomAD LOEUF (loss-of-function intolerance)
0.77
gnomAD pLI
0.02
gnomAD missense Z
0.68
DepMap mean gene effect
0
DepMap dependency class
selective

Cancer expressionTCGA

Across TCGA tumor cohorts, this protein is over-expressed in roughly 2% of surveyed tumor types (aggregate summary; per-cohort expression, alteration, and survival load in the interactive view).

OntologyGO

Biological processes

Cellular components

Protein domainsUniProt · Pfam · InterPro

  • Sperm acrosome membrane-associated protein 1

KeywordsUniProt

InteractionsUniProt · HPA

Protein binding partners of SPACA1 in the human serome: UniProt-annotated complex subunits plus reported interactors. Each links to its own Seroatlas record.

Antibody and autoantibody relevanceSeroatlas analysis

Seroatlas reads SPACA1 as an antibody target. Whether an autoantibody or antibody against SPACA1 could matter depends on whether native SPACA1 is physically reachable, whether the body needs it intact, and whether it acts in a disease-relevant tissue.

SPACA1 is annotated as predominantly intracellular. Intracellular proteins are common autoantibody markers, becoming visible to the immune system after cell injury or altered processing, but are usually markers of disease rather than direct drivers.

Source-annotated serology context

The source annotations explicitly mention antibody, autoantibody, autoantigen, or autoimmune context. This is biological context, not study-specific reactivity.

  • The correlation of anti-sperm antibodies with cases of unexplained infertility implicates a role for these antibodies in blocking fertilization.
  • The protein expressed by this gene is recognized by anti-sperm antibodies from infertile males.
  • Furthermore, antibodies generated against the recombinant protein block in vitro fertilization.

Canonical record: https://seroatlas.com/gene/SPACA1. Study-independent annotations aggregated from UniProt, Human Protein Atlas, PubMed, IEDB, Pfam, InterPro, Gene Ontology, AlphaFold, gnomAD, DepMap, ClinVar, TCGA. Catalog release seroatlas-reviewed-human-uniprot-20260313.

Seroatlas is the reference for exploring autoantibody and antibody serology at the human-protein level: the autoreactome and human serome, multiplex serology (HuProt, HuScan, VirScan, PhIP-Seq).

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