Alpha-lactalbumin

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Lactalbumin, alpha-
PDB rendering based on 1a4v.
Available structures: 1a4v, 1alc, 1b9o, 1hml
Identifiers
Symbol(s) LALBA; MGC138521; MGC138523
External IDs OMIM: 149750 MGI: 96742 HomoloGene: 1720
RNA expression pattern

More reference expression data
Orthologs
Human Mouse
Entrez 3906 16770
Ensembl ENSG00000167531 ENSMUSG00000022991
Uniprot P00709 P29752
Refseq NM_002289 (mRNA)
NP_002280 (protein)		 XM_993980 (mRNA)
XP_999074 (protein)
Location Chr 12: 47.25 - 47.25 Mb Chr 15: 98.31 - 98.31 Mb
Pubmed search [1] [2]

Lactalbumin, alpha-, also known as LALBA, is a human gene.[1]

α-lactalbumin is an important whey protein in cow's milk (~1 g/l), and is also present in many other mammalian species.

The molecular weight is 14176 Da, and the isoelectric point is between 4.2 and 4.5. One of the main structural differences with beta-lactoglobulin is that it does not have any free thiol group that can serve as the starting point for a covalent aggregation reaction. As a result, pure α-lactoglobulin will not form gels upon denaturation and acidification.

When formed into a complex with Gal-T1, a galactosyltransferase, α-lactalbumin enhances the enzymes affinity for glucose by about 1000 times, and inhibits the ability to polymerise multiple galactose units. This gives rise to a pathway for forming lactose by converting Gal-TI to Lactose synthase. The sequence comparison of α-lactalbumin shows a strong similarity to that of lysozymes, specifically the Ca2+-binding c-lysozyme.[2] So the expected evolutionary history is that gene duplication of the c-lysozyme was followed by mutation.[3] This gene predates the last common ancestor of mammals and birds which probably puts its origin at about 300 Ma.[4]

This gene encodes alpha-lactalbumin, a principal protein of milk. Alpha-lactalbumin forms the regulatory subunit of the lactose synthase (LS) heterodimer and beta 1,4-galactosyltransferase (beta4Gal-T1) forms the catalytic component. Together, these proteins enable LS to produce lactose by transfering galactose moieties to glucose. As a monomer, alpha-lactalbumin strongly binds calcium and zinc ions and may possess bactericidal or antitumor activity. A folding variant of alpha-lactalbumin, called HAMLET, likely induces apoptosis in tumor and immature cells.[1]

[edit] References

  1. ^ a b Entrez Gene: LALBA lactalbumin, alpha-.
  2. ^ Acharya KR, Stuart DI, Walker NP, Lewis M, Phillips DC (1989). "Refined structure of baboon alpha-lactalbumin at 1.7 A resolution. Comparison with C-type lysozyme". J. Mol. Biol. 208 (1): 99–127. doi:10.1016/0022-2836(89)90091-0. PMID 2769757. 
  3. ^ Qasba PK, Kumar S (1997). "Molecular divergence of lysozymes and alpha-lactalbumin". Crit. Rev. Biochem. Mol. Biol. 32 (4): 255–306. PMID 9307874. 
  4. ^ Prager EM, Wilson AC (1988). "Ancient origin of lactalbumin from lysozyme: analysis of DNA and amino acid sequences". J. Mol. Evol. 27 (4): 326–35. PMID 3146643. 

[edit] Further reading

  • Heine WE, Klein PD, Reeds PJ (1991). "The importance of alpha-lactalbumin in infant nutrition.". J. Nutr. 121 (3): 277–83. PMID 2002399. 
  • Permyakov EA, Berliner LJ (2000). "alpha-Lactalbumin: structure and function.". FEBS Lett. 473 (3): 269–74. PMID 10818224. 
  • Hall L, Emery DC, Davies MS, et al. (1987). "Organization and sequence of the human alpha-lactalbumin gene.". Biochem. J. 242 (3): 735–42. PMID 2954544. 
  • Davies MS, West LF, Davis MB, et al. (1987). "The gene for human alpha-lactalbumin is assigned to chromosome 12q13.". Ann. Hum. Genet. 51 (Pt 3): 183–8. PMID 3479943. 
  • Findlay JB, Brew K (1972). "The complete amino-acid sequence of human -lactalbumin.". Eur. J. Biochem. 27 (1): 65–86. PMID 5049057. 
  • Hall L, Craig RK, Edbrooke MR, Campbell PN (1982). "Comparison of the nucleotide sequence of cloned human and guinea-pig pre-alpha-lactalbumin cDNA with that of chick pre-lysozyme cDNA suggests evolution from a common ancestral gene.". Nucleic Acids Res. 10 (11): 3503–15. PMID 6285305. 
  • Håkansson A, Zhivotovsky B, Orrenius S, et al. (1995). "Apoptosis induced by a human milk protein.". Proc. Natl. Acad. Sci. U.S.A. 92 (17): 8064–8. PMID 7644538. 
  • Stacey A, Schnieke A, Kerr M, et al. (1995). "Lactation is disrupted by alpha-lactalbumin deficiency and can be restored by human alpha-lactalbumin gene replacement in mice.". Proc. Natl. Acad. Sci. U.S.A. 92 (7): 2835–9. PMID 7708733. 
  • Fujiwara Y, Miwa M, Takahashi R, et al. (1997). "Position-independent and high-level expression of human alpha-lactalbumin in the milk of transgenic rats carrying a 210-kb YAC DNA.". Mol. Reprod. Dev. 47 (2): 157–63. doi:10.1002/(SICI)1098-2795(199706)47:2<157::AID-MRD5>3.0.CO;2-L. PMID 9136116. 
  • Lindner RA, Kapur A, Carver JA (1997). "The interaction of the molecular chaperone, alpha-crystallin, with molten globule states of bovine alpha-lactalbumin.". J. Biol. Chem. 272 (44): 27722–9. PMID 9346914. 
  • Giuffrida MG, Cavaletto M, Giunta C, et al. (1998). "The unusual amino acid triplet Asn-Ile-Cys is a glycosylation consensus site in human alpha-lactalbumin.". J. Protein Chem. 16 (8): 747–53. PMID 9365923. 
  • Chandra N, Brew K, Acharya KR (1998). "Structural evidence for the presence of a secondary calcium binding site in human alpha-lactalbumin.". Biochemistry 37 (14): 4767–72. doi:10.1021/bi973000t. PMID 9537992. 
  • Håkansson A, Andréasson J, Zhivotovsky B, et al. (1999). "Multimeric alpha-lactalbumin from human milk induces apoptosis through a direct effect on cell nuclei.". Exp. Cell Res. 246 (2): 451–60. doi:10.1006/excr.1998.4265. PMID 9925761. 
  • Svensson M, Sabharwal H, Håkansson A, et al. (1999). "Molecular characterization of alpha-lactalbumin folding variants that induce apoptosis in tumor cells.". J. Biol. Chem. 274 (10): 6388–96. PMID 10037730. 
  • Harata K, Abe Y, Muraki M (1999). "Crystallographic evaluation of internal motion of human alpha-lactalbumin refined by full-matrix least-squares method.". J. Mol. Biol. 287 (2): 347–58. doi:10.1006/jmbi.1999.2598. PMID 10080897. 
  • Last AM, Schulman BA, Robinson CV, Redfield C (2001). "Probing subtle differences in the hydrogen exchange behavior of variants of the human alpha-lactalbumin molten globule using mass spectrometry.". J. Mol. Biol. 311 (4): 909–19. doi:10.1006/jmbi.2001.4911. PMID 11518539. 
  • Bai P, Peng Z (2001). "Cooperative folding of the isolated alpha-helical domain of hen egg-white lysozyme.". J. Mol. Biol. 314 (2): 321–9. doi:10.1006/jmbi.2001.5122. PMID 11718563. 
  • Andrews P. "Purification of lactose synthetase a protein from human milk and demonstration of its interaction with alpha-lactalbumin." 9 (5): 297–300. PMID 11947697. 

[edit] External links

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