Reduced Pigmentation (rp, Hps8, Bloc1s3, Blos3)



7qA3. View the map and BAC contig (data from UCSC genome browser).


(assembly 10/03)
Bloc1s3/NM_177692: 2 exons, 1,883 bp, chr7:16,504,517-16,506,399.

The figure below shows the structure of the Bloc1s3 gene (data from UCSC genome browser).

Regulatory Element

Search the 5'UTR and 1kb upstream regions (seq1=human BLOC1S3, seq2=mouse rp) by CONREAL with 80% Position Weight Matrices (PWMs) threshold (view results here).



Bloc1s3/NM_177692: 1,189 bp, view ORF and the alignment to genomic.

Expression Pattern

Tissue specificity: Ubiquitously expressed (by similarity).

Affymetrix microarray expression pattern in SymAtlas from GNF is shown below.



BLOC-1 subunit 3 (NP_808360): 195aa. ExPaSy NiceProt view of Swiss-Prot:Q8C6R4.
Synonyms: Hps8 protein, reduced pigmentation protein, E230011O18 product: hypothetic protein.


Species Human Rat
GeneView BLOC1S3 LOC308413
Protein NP_997715 (202aa) XP_218422 (195aa)
Identities 87%/201aa 93%/195aa

View multiple sequence alignment (PDF file) by ClustalW and GeneDoc.


(1) Domains of predicted by SMART:
a) low complexity: 18 - 51
b) low complexity: 55 - 79
c) low complexity: 126 - 150

(2) Transmembrane domains predicted by SOSUI: none.


(1) Predicted results by ScanProsite:
a) Amidation site : [occurs frequently]
5 - 8: qGRR.

b) Casein kinase II phosphorylation site : [occurs frequently]
22 - 25: TdsE, 29 - 32: SssE, 30 - 33: SseE, 31 - 34: SeeE, 59 - 62: TdsE, 61 - 64: SepE, 111 - 114: TrlD.

c) N-myristoylation site : [occurs frequently]
49 - 54: GLrvAG, 118 - 123: XAavSG, 146 - 151: GLaaAH.

d) Protein kinase C phosphorylation site : [occurs frequently]
152 - 154: SvR.

e) Cell attachment sequence : [occurs frequently]
157 - 159: RGD.

f) Tyrosine sulfation site : [occurs frequently]
29 - 43: ssseeelYlgpsgpt.

(2) Predicted results of subprograms by PSORT II:
a) N-terminal signal peptide: none
b) KDEL ER retention motif in the C-terminus: none
c) ER membrane retention signals: none
d) VAC possible vacuolar targeting motif: none
e) Actinin-type actin-binding motif: type 1: none; type 2: none
f) Prenylation motif: none
g) memYQRL transport motif from cell surface to Golgi: none
h) Tyrosines in the tail: none
i) Dileucine motif in the tail: none

3D Model

(1) ModBase: none.

(2) 3D models predicted by SPARKS (fold recognition) below. View the models by PDB2MGIF.


This protein does not exist in the current release of SWISS-2DPAGE.
Computed theoretical MW=20,445Da, pI=4.84.
The phosphorylated form migrates slower than the unphosphorylated form (Gwynn, et al).



(1) May play a role in intracellular vesicle trafficking.
(2) Protein interaction in BLOC-1.




BLOC-1 subunit 3 is a subunit of the biogenesis of lysosome-related organelles complex 1 (BLOC-1), which resides with the products of seven other HPS genes, sdy, mu, pa, cno, Snapap, Blos1, Blos2 (Ciciotte, et al; Falcon-Perez , et al; Li, et al; Moriyama, et al; Starcevic, et al). It interacts with Blos2 within the complex ( Starcevic, et al) (view diagram of BLOC-1 complex here). More details about the function of BLOC-1 are described in the HPS7 profile.


Involved in the development of lysosome-related organelles, such as melanosomes and platelet-dense granules (view diagram of BLOC-1 pathway here). Nguyen, et al found that the maturation of melanosomes is blocked in early stages (view diagram of melanosome blockage here).


Allele or SNP

1 phenotypic allele is described in MGI:2678952.

SNPs deposited in dbSNP.


Location Genomic cDNA Protein Type Strain Reference
Exon 2 238C>T 238C>T Q80X nonsense rp (B6) Starcevic, et al
(Numbering of cDNA sequence is based on the start codon of RefSeq NM_177692.)


The Q80X mutation is not subject to nonsense mediated decay, but no detectable Blos3 protein in liver extracts of rp mutants. The mutation does affect the stability of other subunits such as pallidin and muted of BLOC-1 complex, but does not completely disrupt BLOC-1 assembly (Starcevic, et al).


Mutation in the Bloc1s3 gene is the cause of reduced pigmentation (rp) mutant (Starcevic, et al). The rp allele arose from C57BL/Tb. The strain is described in more detail in JAX Mice database (C57BL-Bloc1s1rp/J) Homozygotes have a hypopigmented coat color and show phenotypic similarity to human Hermansky-Pudlak Syndrome (Gibb, et al; Swank, et al). The rp mice exhibit a less pronounced pigmentation defect than pallid mice, suggesting that rp mice may retain some residual BLOC-1 function (Starcevic, et al). The phenotype is described in more detailin Mouse Locus Catalog#Bloc1s3. Both double homozygotes of rp/rp-cno/cno and rp/rp-pa/pa do not show exacerbation of the HPS phenotype compared to the single mutants. However, doubly homozygous offspring (rp/rp-ru/ru) shows an exacerbated coat-color phenotype compared to either single homozygotes alone, which suggests that BLOC-1 and BLOC-2 define functionally independent pathways in the biogenesis of LROs (Gwynn, et al).


  1. Ciciotte SL, Gwynn B, Moriyama K, Huizing M, Gahl WA, Bonifacino JS, Peters LL. Cappuccino, a mouse model of Hermansky-Pudlak syndrome, encodes a novel protein that is part of the pallidin-muted complex (BLOC-1). Blood 2003; 101: 4402-7. PMID: 12576321
  2. Falcon-Perez JM, Starcevic M, Gautam R, Dell'Angelica EC. BLOC-1, a novel complex containing the pallidin and muted proteins involved in the biogenesis of melanosomes and platelet-dense granules. J Biol Chem 2002; 277: 28191-9. PMID: 12019270
  3. Gibb S, Hakansson EM, Lundin LG, Shire JG. Reduced pigmentation (rp), a new coat colour gene with effects on kidney lysosomal glycosidases in the mouse. Genet Res 1981; 37: 95-103. PMID: 7203014
  4. Gwynn B, Martina JA, Bonifacino JS, Sviderskaya EV, Lamoreux ML, Bennett DC, Moriyama K, Huizing M, Helip-Wooley A, Gahl WA, Webb LS, Lambert AJ, Peters LL. Reduced pigmentation (rp), a mouse model of Hermansky-Pudlak syndrome, encodes a novel component of the BLOC-1 complex. Blood 2004; 104: 3181-9. PMID: 15265785
  5. Li W, Zhang Q, Oiso N, Novak EK, Gautam R, O'Brien EP, Tinsley CL, Blake DJ, Spritz RA, Copeland NG, Jenkins NA, Amato D, Roe BA, Starcevic M, Dell'Angelica EC, Elliott RW, Mishra V, Kingsmore SF, Paylor RE, Swank RT. Hermansky-Pudlak syndrome type 7 (HPS-7) results from mutant dysbindin, a member of the biogenesis of lysosome-related organelles complex 1 (BLOC-1). Nat Genet 2003; 35: 84-9. PMID: 12923531
  6. Moriyama K, Bonifacino JS. Pallidin is a component of a multi-protein complex involved in the biogenesis of lysosome-related organelles. Traffic 2002; 3: 666-77. PMID: 12191018
  7. Nguyen T, Novak EK, Kermani M, Fluhr J, Peters LL, Swank RT, Wei ML. Melanosome morphologies in murine models of hermansky-pudlak syndrome reflect blocks in organelle development. J Invest Dermatol 2002; 119: 1156-64. PMID: 12445206
  8. Starcevic M, Dell'Angelica EC. Identification of snapin and three novel proteins (BLOS1, BLOS2, and BLOS3/reduced pigmentation) as subunits of biogenesis of lysosome-related organelles complex-1 (BLOC-1). J Biol Chem 2004; 279: 28393-401. PMID: 15102850
  9. Swank RT, Novak EK, McGarry MP, Rusiniak ME, Feng L. Mouse models of Hermansky Pudlak syndrome: a review. Pigment Cell Res 1998; 11: 60-80. PMID: 9585243

Created by Wei Li, 07/08/2004
Updated by Wei Li, 08/03/2012

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