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Contents 1 Alpha Lactalbumin 2 Structure 3 Function 4 Recent Studies 5 References

Alpha Lactalbumin

α-lactalbumin is a major protein in all kinds of milk studied so far. ^[1] α- lactalbumin contributes to cell lytic activity, cell growth inhibition, and apoptosis but most importantly, it interacts with UDP-galactosyltransferase ^[1] to form lactose synthetase via the following reaction:

UDP-galactose + glucose -+ lactose + UDP ^[2]

spinqualitylabelsall models PDB ID 1a4v Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image
1a4v, resolution 1.80Å ()
Ligands:
Activity:	Lactose synthase, with EC number 2.4.1.22
Structural annotation: Resources: CATH : 1A4V000 InterPro : Ipr000545, Ipr001916 Pfam : PF00062 SCOP : d1a4v__ UniProt : P00709
Functional annotation: Cellular component: extracellular region extracellular space Biological process: signal transduction lactose biosynthetic process cell-cell signaling defense response to bacterium induction of apoptosis Molecular function: lactose synthase activity calcium ion binding
Evolutionary conservation: Toggle Conservation Colors: Rows = identical sequences: Further Information: Caveats, Explanation, Complete Results at ConSurfDB
Resources:	FirstGlance, OCA, PDBsum, RCSB
Coordinates:	save as pdb, mmCIF, xml

Structure

α-lactalbumin is a small globular protein which is stabilized by four disulfide bonds with two structural domains. One domain is rich in α-helices, the other is rich in β-sheets and has a calcium binding site. ^[3]

: with alpha helices shown in pink rockets, and beta sheets shown in yellow planks.

: with nonpolar side chains in gray, polar side chains in purple, and associated water molecules in red.

: calcium ligands with amino acid contacts. water in pink, oxygen in red.

:cations in blue, anions in red, hydrophobic in gray, polar uncharged in light purple, backbone in dark purple.

Function

Recent Studies

Tryptophan is component of many alpha-lactalbumin proteins ^[4], the availability of which changes the ratio of plasma tryptophan to the sum of larger neutral amino acids (Trp-LNAA ratio). Tryptophan is a serotonin precursor and proper serotonin function in the brain has been shown to promote sleep regulation and cognitive processes. ^[5] Deficient serotonin function, possibly from chronic stress ^[4], can result in difficulty sleeping and therefore behavioral decline. Recent studies have shown that consumption of alpha-lactalbumin protein with enriched tryptophan content caused increased alertness and performance the morning after ^[5].

References

1. ↑ ^{1.0 1.1} Vilotte JL. Alpha-lactalbumin: Gene Structure and Expression. <http://mammary.nih.gov/Reviews/gene_expression/Vilotte001/index.html>.
2. ↑ Fitzgerald DK, Brodbeck URS, Kiyosawa I, Mawal R, Colvin B, Ebner KE. 1970. α-lactalbumin and the Lactose Synthetase Reaction. The Journal of Biological Chemistry. 245(8): 2103-2108.
3. ↑ Hendrix TM, Griko Y, Privalov P. 1996. Energetics of structural domains in α-lactalbumin. Protein Science. 5923-5931.
4. ↑ ^{4.0 4.1} Markus CR, Olivier B, de Haan EH. 2002. Whey protein rich in alpha-lactalbumin increases the ratio of plasma tryptophan to the sum of the other larger neutral amino acids and improves cognitive performance in stress vulnerable subjects. Am J Clin Nutr. 75(6):1051-1056.
5. ↑ ^{5.0 5.1} Markus CR, Jonkman LM, Lammers JH, Deutz NE, Messer MH, Rigtering N. 2005. Evening intake of alpha-lactalbumin increases plasma tryptophan availability and improves morning alertness and brain measures of attention. Am J Clin Nutr. 81(5):1026-1033.