BACKGROUND: Protein tyrosine kinases are involved in signal transduction
pathways that regulate cell growth, differentiation, activation and
transformation. Human lymphocyte specific kinase (Lck) is a 56 kDa protein
involved in T-cell- and IL2-receptor signaling. Three-dimensional structures are
known for SH3, SH2 and kinase domains of Lck as well as for other tyrosine
kinases. No structure is known for the unique domain of any Src-type tyrosine
kinase. RESULTS: Lck(1-120) comprising unique and SH3 domains was structurally
investigated by nuclear magnetic resonance spectroscopy. We found the unique
domain, in contrast to the SH3 part, to have basically no defined structural
elements. The solution structure of the SH3 part could be determined with very
high precision. It does not show significant differences to Lck SH3 in the
absence of the unique domain. Minor differences were observed to the X-ray
structure of Lck SH3. CONCLUSION: The unique domain of Lck does not contain any
defined structure elements in the absence of ligands and membranes. Presence of
the unique domain is not relevant to the three-dimensional structure of the Lck
SH3 domain.
