Albany 2001

category image Biomolecular
SUNY at Albany
June 19-23, 2001

Water Soluble Heteropolymers

Sequences of the present day proteins are widely believed to result from evolution selection. One of the simplest aspects of selective pressure is the requirement that (globular) proteins must be water soluble. It is well known that proteins solve solubility problem by having the hydrophilic envelope surrounding their hydrophobic core, which, in turn, provides for compactness of the globule. It has been known for decades that this "microsegregated" structure implies certain overall hydrophobic/hydrophilic composition of the sequences dictated essentially by the surface to volume ratio of the folded globule. In this work, we discuss further requirements imposed on the sequence by the condition that microsegregated globular conformation must be accessible. We first address this problem using the non-specific sequence design approach suggested in ref. (1). We show, that for flexible polymers solubility condition leads to sequences with long range correlations of the Levy flight type (2). This model can be called Gaussian, because it arises from Gaussian statistics of conformations inside the globule. We further discuss the applicability of Gaussian model in the light of loop lengths statistics in Protein Data Base (3). This allows us to incorporate the corrections to the Gaussian-related statistics of sequences due to the elements of secondary structure. Finally, we address the question of sequence space entropy, which is essentially the number of sequences which can make it for water soluble heteropolymer globule.

References and Footnotes
  1. A.R.Khokhlov, P.G.Khalatur, Physica A 249, 253-257 (1998)
  2. E.N.Govorun, et al, preprint,http://xxx.lanl.gov/abs/cond-mat/0102180
  3. I.N.Berezovsky, A.Y.Grosberg, E.N.Trifonov, FEBS Letters 466,283-286 (2000)

Alexander Grosberg

Department of Physics, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455, USA and Institute of Biochemical Physics, Russian Academy of Sciences, Moscow 117977, Russia
Phone: 1(612)624-7542; Fax: 1(612)626-8606; grosberg@physics.umn.edu