Alpha-lactalbumin

Lactalbumin, alpha-, also known as LALBA, is a human gene.cite web | title = Entrez Gene: LALBA lactalbumin, alpha-| url = http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=3906| accessdate = ]

α-lactalbumin is an important whey protein in cow's milk (~1 g/l), and is also present in the milk of 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-lactalbumin 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.cite journal | author = Acharya KR, Stuart DI, Walker NP, Lewis M, Phillips DC | title = Refined structure of baboon alpha-lactalbumin at 1.7 A resolution. Comparison with C-type lysozyme | journal = J. Mol. Biol. | volume = 208 | issue = 1 | pages = 99–127 | year = 1989 | pmid = 2769757 | doi = 10.1016/0022-2836(89)90091-0 | issn = ] So the expected evolutionary history is that gene duplication of the c-lysozyme was followed by mutation.cite journal | author = Qasba PK, Kumar S | title = Molecular divergence of lysozymes and alpha-lactalbumin | journal = Crit. Rev. Biochem. Mol. Biol. | volume = 32 | issue = 4 | pages = 255–306 | year = 1997 | pmid = 9307874 | doi = | issn = ] This gene predates the last common ancestor of mammals and birds which probably puts its origin at about 300 Ma.cite journal | author = Prager EM, Wilson AC | title = Ancient origin of lactalbumin from lysozyme: analysis of DNA and amino acid sequences | journal = J. Mol. Evol. | volume = 27 | issue = 4 | pages = 326–35 | year = 1988 | pmid = 3146643 | doi = | issn = ]

PBB_Summary
section_title =
summary_text = 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.cite web | title = Entrez Gene: LALBA lactalbumin, alpha-| url = http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=3906| accessdate = ]

References

Further reading

PBB_Further_reading
citations =
*cite journal | author=Heine WE, Klein PD, Reeds PJ |title=The importance of alpha-lactalbumin in infant nutrition. |journal=J. Nutr. |volume=121 |issue= 3 |pages= 277–83 |year= 1991 |pmid= 2002399 |doi=
*cite journal | author=Permyakov EA, Berliner LJ |title=alpha-Lactalbumin: structure and function. |journal=FEBS Lett. |volume=473 |issue= 3 |pages= 269–74 |year= 2000 |pmid= 10818224 |doi=
*cite journal | author=Hall L, Emery DC, Davies MS, "et al." |title=Organization and sequence of the human alpha-lactalbumin gene. |journal=Biochem. J. |volume=242 |issue= 3 |pages= 735–42 |year= 1987 |pmid= 2954544 |doi=
*cite journal | author=Davies MS, West LF, Davis MB, "et al." |title=The gene for human alpha-lactalbumin is assigned to chromosome 12q13. |journal=Ann. Hum. Genet. |volume=51 |issue= Pt 3 |pages= 183–8 |year= 1987 |pmid= 3479943 |doi=
*cite journal | author=Findlay JB, Brew K |title=The complete amino-acid sequence of human -lactalbumin. |journal=Eur. J. Biochem. |volume=27 |issue= 1 |pages= 65–86 |year= 1972 |pmid= 5049057 |doi=
*cite journal | author=Hall L, Craig RK, Edbrooke MR, Campbell PN |title=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. |journal=Nucleic Acids Res. |volume=10 |issue= 11 |pages= 3503–15 |year= 1982 |pmid= 6285305 |doi=
*cite journal | author=Håkansson A, Zhivotovsky B, Orrenius S, "et al." |title=Apoptosis induced by a human milk protein. |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=92 |issue= 17 |pages= 8064–8 |year= 1995 |pmid= 7644538 |doi=
*cite journal | author=Stacey A, Schnieke A, Kerr M, "et al." |title=Lactation is disrupted by alpha-lactalbumin deficiency and can be restored by human alpha-lactalbumin gene replacement in mice. |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=92 |issue= 7 |pages= 2835–9 |year= 1995 |pmid= 7708733 |doi=
*cite journal | author=Fujiwara Y, Miwa M, Takahashi R, "et al." |title=Position-independent and high-level expression of human alpha-lactalbumin in the milk of transgenic rats carrying a 210-kb YAC DNA. |journal=Mol. Reprod. Dev. |volume=47 |issue= 2 |pages= 157–63 |year= 1997 |pmid= 9136116 |doi= 10.1002/(SICI)1098-2795(199706)47:2<157::AID-MRD5>3.0.CO;2-L |doilabel=10.1002/(SICI)1098-2795(199706)47:2157::AID-MRD53.0.CO;2-L
*cite journal | author=Lindner RA, Kapur A, Carver JA |title=The interaction of the molecular chaperone, alpha-crystallin, with molten globule states of bovine alpha-lactalbumin. |journal=J. Biol. Chem. |volume=272 |issue= 44 |pages= 27722–9 |year= 1997 |pmid= 9346914 |doi=
*cite journal | author=Giuffrida MG, Cavaletto M, Giunta C, "et al." |title=The unusual amino acid triplet Asn-Ile-Cys is a glycosylation consensus site in human alpha-lactalbumin. |journal=J. Protein Chem. |volume=16 |issue= 8 |pages= 747–53 |year= 1998 |pmid= 9365923 |doi=
*cite journal | author=Chandra N, Brew K, Acharya KR |title=Structural evidence for the presence of a secondary calcium binding site in human alpha-lactalbumin. |journal=Biochemistry |volume=37 |issue= 14 |pages= 4767–72 |year= 1998 |pmid= 9537992 |doi= 10.1021/bi973000t
*cite journal | author=Håkansson A, Andréasson J, Zhivotovsky B, "et al." |title=Multimeric alpha-lactalbumin from human milk induces apoptosis through a direct effect on cell nuclei. |journal=Exp. Cell Res. |volume=246 |issue= 2 |pages= 451–60 |year= 1999 |pmid= 9925761 |doi= 10.1006/excr.1998.4265
*cite journal | author=Svensson M, Sabharwal H, Håkansson A, "et al." |title=Molecular characterization of alpha-lactalbumin folding variants that induce apoptosis in tumor cells. |journal=J. Biol. Chem. |volume=274 |issue= 10 |pages= 6388–96 |year= 1999 |pmid= 10037730 |doi=
*cite journal | author=Harata K, Abe Y, Muraki M |title=Crystallographic evaluation of internal motion of human alpha-lactalbumin refined by full-matrix least-squares method. |journal=J. Mol. Biol. |volume=287 |issue= 2 |pages= 347–58 |year= 1999 |pmid= 10080897 |doi= 10.1006/jmbi.1999.2598
*cite journal | author=Last AM, Schulman BA, Robinson CV, Redfield C |title=Probing subtle differences in the hydrogen exchange behavior of variants of the human alpha-lactalbumin molten globule using mass spectrometry. |journal=J. Mol. Biol. |volume=311 |issue= 4 |pages= 909–19 |year= 2001 |pmid= 11518539 |doi= 10.1006/jmbi.2001.4911
*cite journal | author=Bai P, Peng Z |title=Cooperative folding of the isolated alpha-helical domain of hen egg-white lysozyme. |journal=J. Mol. Biol. |volume=314 |issue= 2 |pages= 321–9 |year= 2001 |pmid= 11718563 |doi= 10.1006/jmbi.2001.5122
*cite journal | author=Andrews P |title=Purification of lactose synthetase a protein from human milk and demonstration of its interaction with alpha-lactalbumin. |journal= |volume=9 |issue= 5 |pages= 297–300 |year= |pmid= 11947697 |doi=

External links

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