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α-lactalbumin [1], a milk protein, is the regulatory subunit of lactose synthase. In the mammary gland, α-lactalbumin changes the substrate specificity of galactosyltransferase from N-acetylglucosamine to glucose.

Lysozymes (EC 3.2.1.17) [2] act as bacteriolytic enzymes by hydrolyzing the β(1->4) bonds between N-acetylglucosamine and N-acetylmuramic acid in the peptidoglycan of prokaryotic cell walls. There are at least five different classes of lysozymes [3,4]: C (chicken type), G (goose type), phage-type (T4), fungi (Chalaropsis), and bacterial (Bacillus subtilis) but there are few similarities in the sequences of the different types of lysozymes.

α-lactalbumin and lysozyme C are evolutionary related [5]. Around 35 to 40% of the residues are conserved in both proteins as well as the positions of the four disulfide bonds (see the schematic representation). The pattern for this family of proteins includes three cysteines involved in two of these disulfide bonds (the first cysteine is linked to the third one).

                                  +-------+
                                  |     **|*******
     xxCxxxxxxxxxxCxxxxxxxxxxxxxxxCxxxxxCxCxxxxxxCxxxxxxxxxCxxxCxx
       |          |                     +--------+         |    |
       |          +----------------------------------------+    |
       +--------------------------------------------------------+

'C': conserved cysteine involved in a disulfide bond.
'*': position of the pattern.

We also developed a profile that covers the entire α-lactalbumin / lysozyme C.

These proteins belong to family 22 in the classification of glycosyl hydrolases [6,E1].

December 2007 / Text revised; profile added.

PROSITE methods (with tools and information) covered by this documentation:

LACTALBUMIN_LYSOZYME_2, PS51348; Alpha-lactalbumin / lysozyme C family profile  (MATRIX)

Sequences known to belong to this class detected by the profile: ALL Other sequence(s) detected in Swiss-Prot: NONE.

• Domain architecture view of Swiss-Prot proteins matching PS51348 • Retrieve an alignment of Swiss-Prot true positive hits:   Clustal format, color, condensed view  / Clustal format, color  / Clustal format, plain text  / Fasta format • Retrieve the sequence logo from the alignment • Taxonomic tree view of all Swiss-Prot/TrEMBL entries matching PS51348 • Retrieve a list of all Swiss-Prot/TrEMBL entries matching PS51348 • Scan Swiss-Prot/TrEMBL entries against PS51348 • view ligand binding statistics

Matching PDB structures: 132L 133L 134L 135L ... [ALL]

LACTALBUMIN_LYSOZYME_1, PS00128; Alpha-lactalbumin / lysozyme C signature  (PATTERN)

Consensus pattern: C-x(3)-C-x(2)-[LMF]-x(3)-[DEN]-[LI]-x(5)-C The 3 C's are involved in disulfide bonds Sequences known to belong to this class detected by the pattern: ALL Other sequence(s) detected in Swiss-Prot: NONE.

• Retrieve an alignment of Swiss-Prot true positive hits:   Clustal format, color, condensed view  / Clustal format, color  / Clustal format, plain text  / Fasta format • Retrieve the sequence logo from the alignment • Taxonomic tree view of all Swiss-Prot/TrEMBL entries matching PS00128 • Retrieve a list of all Swiss-Prot/TrEMBL entries matching PS00128 • Scan Swiss-Prot/TrEMBL entries against PS00128 • view ligand binding statistics

Matching PDB structures: 132L 133L 134L 135L ... [ALL]

1	Authors	Hall L., Campbell P.N.
	Title	Alpha-lactalbumin and related proteins: a versatile gene family with an interesting parentage.
	Source	Essays Biochem. 22:1-26(1986).
	PubMed ID	3104032

2
Source	Concise Encyclopedia Biochemistry, Second Edition, Walter de Gruyter, Berlin New-York (1988).

3	Authors	Weaver L.H., Grutter M.G., Remington S.J., Gray T.M., Isaacs N.W., Matthews B.W.
	Source	J. Mol. Evol. 21:97-111(1985).

4	Authors	Kamei K., Hara S., Ikenaka T., Murao S.
	Title	Amino acid sequence of a lysozyme (B-enzyme) from Bacillus subtilis YT-25.
	Source	J. Biochem. 104:832-836(1988).
	PubMed ID	3148618

5	Authors	Nitta K., Sugai S.
	Title	The evolution of lysozyme and alpha-lactalbumin.
	Source	Eur. J. Biochem. 182:111-118(1989).
	PubMed ID	2731545

6	Authors	Henrissat B.
	Title	A classification of glycosyl hydrolases based on amino acid sequence similarities.
	Source	Biochem. J. 280:309-316(1991).
	PubMed ID	1747104

E1
Source	http://www.uniprot.org/docs/glycosid

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